10 th International Myopia conference , Cambridge 2004 - abstract book

The Cambridge Garden House Hotel

Proceedings

From: Logan, N. S., Gilmartin, B., Wildsoet, C. F. and Dunne, M. C. M. (2004). Posterior retinal contour in adult human anisomyopia. Invest. Ophthalmol. Vis. Sc. 45: 2152 – 2162. With the kind permission of the authors and publishers.

Anglia Polytechnic University, Cambridge, United Kingdom

Vision CRC, University of New South Wales, Sydney, Australia.

Proceedings of the 10th International Myopia Conference 19th – 22nd July 2004 Cambridge, UK

Edited by Daniel J O’Leary and Hema Radhakrishnan

Published by APU, Cambridge, 2004 ISBN: 0-907262-67-8

10th International myopia conference 2004

Contents: Welcome!

3

Organising Committee

3

International Committee

4

Conference timetable

5-9

Monday Tuesday lecture presentations Tuesday Poster Session Wednesday Thursday Abstracts Monday afternoon Tuesday session 1 Tuesday session 2 Tuesday session 3 Tuesday Posters Wednesday session 1 Wednesday session 2 Wednesday session 3 Thursday morning

10-15 16-18 19-21 22-25 26-37 38-40 41-43 44-47 48-52

Author index

53-54

2

5 6 7 8 9


Welcome! On behalf of Anglia Polytechnic University, the Vision Co-operative Research Centre and the Committee of the International Conferences on Myopia, welcome to Cambridge, and welcome to the 10th International Myopia Conference. In our venue at the Garden House Hotel you are only a few hundred yards from the places where the electron was discovered by JJ Thomson and the structure of DNA was discovered by Crick and Watson. I hope the science we discuss over the next few days may one day be as famous as these discoveries. As well as enjoying the science we hope you enjoy the city too. It is a pleasure to wander round the colleges and the backs. You will see the colleges at their best from a guided punt-tour from Magdalene Bridge, although the brave may try to punt themselves – be careful! It is harder than it looks! You can walk along the river from here for about 20 miles as far as Ely, where one of the great Norman Cathedrals of Europe is open for all its glories to be seen. (Those in a hurry can take a train from Cambridge, which takes about 20 minutes.) Back in Cambridge, look in at the Eagle Pub in Bene’t Street, frequented by many scientists over the years and enjoy the many restaurants and bars scattered through the city. Heffer’s book-shop in Trinity Street serves the University community as well as the public. If you leave the hotel and walk south you can follow the river to Grantchester and Byron’s pool, and see the village church referred to in Rupert Brooke’s famous poem. But most of all we hope you enjoy the conference and find the presentations stimulating and inspiring. Thank you all for making the effort to travel here to Cambridge and make the conference a success. Daniel O’Leary. Organising Committee: Daniel J. O’Leary

Hema Radhakrishnan

3

Shahina Pardhan


International Conference on Myopia Committee:

Hans C. Fledelius, Rigshospitalet, Denmark Ian Flitcroft, University of Dublin, Ireland Bernard Gilmartin, Aston University, UK Ernst W.M. Goldschmidt., Hilleroed Sygehus, Denmark Jane Gwiazda, The New England College of Optometry, USA Brien Holden, University of New South Wales, Australia Thomas T. Norton, The University of Alabama at Brimingham, USA Daniel J. O’Leary, Anglia Polytechnic University, UK Shahina Pardhan, Anglia Polytechnic University, UK Hema Radhakrishnan, Anglia Polytechnic University, UK Jacob Sivak, University of Waterloo, Canada Earl Smith, University of Houston, USA Elena Tarutta, Helmholtz Research Institute of Eye Diseases, Russia. Josh Wallman, City University of New York, USA Brian Ward, Stanford University Medical Center, USA Maurice Yap, The Hong Kong Polytechnic University, Hong Kong

4


11.00 – 11.30

Monday 19th July Registration and coffee at the Riverside GRANTA SUITE Welcome

11.30 – 12.30

Dr. Richard A. Stone: Chew Sek-jin Memorial lecture

12.30 – 14.00

Lunch in Garden House Buffet and gardens

9.00 - 11.00

Physiological Optics 1 Co-chairs: Dr Maurice Yap and Dr Bernard Gilmartin 14.00 – 14.30 14.30 – 14.50 14.50 – 15.10 15.10 – 15.30 15.30 – 16.00 16.00 – 16.20 16.20 – 16.40 16.40 – 17.00 17.00 –17.20 17.20 – 17.40

Keynote speaker Dr Bernard Gilmartin : Myopia: pathways to therapy Dr. Karla Zadnik : Accommodative lag at the onset of myopia in children. Dr. Leon Davies : Effect of cognition and refractive error on oculomotor and cardiovascular function. Dr. Elise Harb : Behavioral characteristics of accommodation during periods of sustained reading. Coffee Dr. Nicola Logan : Ametropia and ocular biometry in a UK undergraduate population. Dr. Patrick Ting : Instrument myopia during microscopy and factors affecting it. Dr. Leon Davies: Autonomic correlates of oculomotor and cardiovascular function in myopic subjects. Dr. Hema Radhakrishnan: Spherical aberration and accommodation Dr. Peter M. Allen: Accommodation dysfunction and myopia progression in young adults

5


Tuesday 20th July Animal Studies and Physiological Optics 2 Session 1: 9.00 – 10.30 Co-chairs Dr Earl Smith III and Dr Jacob Sivak 9.00 – 9.30 9.30 - 9.50 9.50 – 10.10 10.10 -10.30 10.30 – 11.00

11.00 - 11.30

11.30 - 11.50 11.50 – 12.10 12.10 -12.30 12.30 – 12.50 12.50 – 14.00

Keynote Speaker Dr. Earl Smith III Animal Models and Human Refractive Errors Dr. Dolores Bradley: Form deprivation myopia in juvenile and adult rhesus monkeys (Macaca mulatta). Dr. Thomas Norton: The effect of plus lenses on the visual guidance of axial elongation and refractive state in tree shrews. Dr. John Potter: Long term blur adaptation measured from visual evoked potentials Coffee

Session 2: 11.00 – 12.50 Co-chairs Dr Josh Wallman and Dr Katrina Schmid Keynote Speaker: Dr. Josh Wallman Temporal and spatial aspects of visual guidance of eye growth Mr. Ramkumar Ramamirtham: Wave aberrations in rhesus monkeys with visininduced ametropias. Dr. Howard Howland: High order wave aberration of chicks due to constant light rearing and its recovery. Dr. Elena Iomdina: Failure of limited proteolysis of pigment epithelium-derived factor (PEDF) in Tenon’s capsule of children with progressive myopia Dr. Katrina Schmid: The effects of GABA-B and GABA-C antagonists on myopia development in chick. Lunch in Garden House Buffet and gardens

Session 3: 2.00pm – 5.00pm Co-chairs Dr Thomas Norton and Dr Pauline Cho 14.00 – 14.30

Keynote Speaker Dr. Thomas Norton: Signalling Mechanisms in Choroid and Sclera

14.30 – 14.50

Dr. Jacob G. Sivak: Effect of Hyperbaric Oxygen on Guinea Pig Lens Optical Quality and on the Development of Myopia

14.50 – 15.10

Dr. Pauline Cho: The longitudinal orthokeratology research in children (LORIC) study in Hong Kong. A pilot study on refractive changes and myopia control. Ms. Sin Wang Cheung: Refractive error and visual acuity changes in orthokeratology patients. Coffee Dr. Ivan Wood: Vision screening for myopia and other target conditions in South Auckland AIMHI schools Dr. Yury Rosenblum: A one-year follow–up study of refraction, accommodation and axial length of schoolchildren in the far north region Dr. Niall Strang: Psychophysical measurements of blur thresholds in myopes and emmetropes

15.10 – 15.30 15.30 - 16.00 16.00 - 16.20 16.20 – 16.40 16.40 – 17.00

6


Tuesday 17.00 – 18.30 Poster session in the Cam Suite 1. Dr. Andrew Collins 2. Dr. Elena Tarutta 3. Dr. Elena Tarutta 4. Dr. Elena Tarutta 5. Dr. Elena Tarutta 6. Dr. Narine Khodzhabekyan 7. Dr. Narine Khodzhabekyan 8. Dr. Gayane Markossian 9. Dr. Gayane Markossian 10. Dr. Thomas Aller 11. Dr. Yury Rosenblum 12. Dr. Rafaela Garrido 13. Dr. Edward Mallen 14. Dr. Mhairi Day 15. Dr. Dirk Seidel 16. Dr. Richard McCollim 17.Dr. J. Guggenheim 18. Dr. Tatyana Verjanskaya 19. Mr. Ashok Pandian 20. Dr. Chuen Lam 21. Dr. Patrick WK Ting 22. Dr. Elena Iomdina 23. Dr. A.A. Yekta

Visual acuity and guiding performance in a group of guide dogs: Effect of naturallyoccurring myopia The state of eye fundus in children and adolescents with congenital myopia Acoustical Density of the Sclera as a Prognostic Factor of the Clinical Course of Myopia Low power lasers in the treatment of low and moderate progressive myopia An inhibitory effect of penalization (hyperopic overcorrection) on eye growth and refractogenesis The x-ray density of sclera and shape of the eyes with myopic refraction The muscular balance of eyes and AC/A ratio in patients with myopic anisometropia Functional state of the retina in children with congenital myopia Linkage analysis for some myopia loci in Russian families with autosomal dominant complicated high myopia Design of a prospective clinical trial of the use of bifocal soft contact lenses to control myopia progression (CONTROL) Acquired progressive eso- and hypotropia in high myopia Prevalence of refractive errors in university students The influence of lighting on accommodation responses in emmetropes and myopes Target vergence related increases in accommodation microfluctuations in myopia and emmetropia Voluntary Accommodation Responses in Emmetropia and Myopia A Unique Case of Self-induced Myopia and Monocular Diplopia A cross-sectional study of anisometropia Changes in main anatomical and optical characteristics of the eye during overnight orthokeratology lens wear. Facility of accommodation in children with and without Myopia. Differential protein expressions in the emmetropisation of chick eyes Longitudinal study of myopia progression of Hong Kong Chinese microscopists Remote results of local antioxidant treatment of progressive myopia A cross sectional study of the effect of age on myopia

7


Wednesday 21st July Clinical Studies Session 1: 9.00-10.30 Co-chairs Dr Jane Gwiazda and Dr Karla Zadnik 9.00 – 9.30 9.30 – 9.50 9.50 – 10.10 10.10 – 10.30 10.30 – 11.00 11.00 – 11.30

11.30 – 11.50 11.50 – 12.10 12.10 – 12.20 12.30 – 12.50 12.50 – 14.00

14.00 – 14.30

14.30 – 14.50 14.50 – 15.10 15.10 – 15.30 15.30 – 16.00 16.00 – 16.30 16.30 – 16.50 16.50 – 17.10

Keynote Speaker: Dr. Jane Gwiazda. Clinical trials of lens treatments for myopia control Dr. Desmond Cheng: The prevalence and progression of myopia in ChineseCanadian children attending an optometric practice Dr. John Phillips. Spectacle lens defocus alters myopia progression rate in schoolchildren Dr. Karla Zadnik. Prediction of myopia beyond the influences of refractive error Coffee

Session 2: 11.00 – 12.50 Co-chairs Dr Ernst Goldschmidt and Dr Saw Seang Mei Keynote Speaker: Dr. Ernst Goldschmidt. Myopia and environment Dr. Takashi Fujikado. The long-term effect of macular translocation surgery with 360-degree retinotomy for myopic choroidal neovascularization Dr. Brian Ward. Degenerative myopia, the risk of visual disability and the identification of criteria for therapeutic intervention. Dr. Elena Tarutta: Progressive myopia in children: To cure or not to cure? Dr. Seang-Mei Saw: Is IQ associated with myopia in children? Lunch in Garden House Buffet and gardens

Session 3: 2.00 – 5.10 Co-chairs Dr Terri Young and Dr Ian Morgan Keynote Speaker Dr. T L Young. Progress In the Molecular Genetics of High Myopia Dr. WC Tang. Testing for association between MYOC and myopia susceptibility in Hong Kong Chinese population. Dr. Paul Baird. Methodology of the genes in myopia (GEM) study Dr. S.P. Yip A systematic unifying approach to identifying myopia susceptibility genes. Coffee Dr. Ian Morgan: How genetic is school myopia? Dr. CJ Hammond. A genome-wide linkage analysis suggests PAX6 is linked to myopia in a sample of dizygotic twins Dr. Martin Hergersberg . The gene encoding fibulin-1 (FBLN1): A candidate gene for early-onset high myopia with recessive inheritance

8


Thursday 22nd July: 9.00-12.30 Physiological Optics 3 Co-chairs Dr Neil Charman and Dr Howard Howland 9.00 – 9.30 9.30 – 9.50 9.50 – 10.10 10.10 – 10.30 10.30 – 11.00 11.00 – 11.20 11.20 – 11.40 11.40 – 12.00 12.00 – 12.20 12.20 12.30

Keynote Speaker: Dr. Neil Charman. Ocular aberrations Dr. WCK Kwan. A Longitudinal Study of Monochromatic aberrations Change in Children with Increasing Myopia Dr. Hans Fledelius The noble art of measuring axial eye length: A mini-survey, to include also the utility of the IOL-Master Dr. Yoshinori Nakai . The relation between growth of axial length and higher order aberrations in school children. Coffee Dr. Gregor Schmid. Retinal steepness vs. myopic shift in children Dr. Mark Bullimore. Should axial length measured with the IOL-Master become the primary outcome measure in clinical trials of myopia progression? Dr. Hans Fledelius. Myopia is axial until otherwise proven: A discussion of clinical entities apparently at variance Dr. Daniel J. O’Leary. Spherical aberration and refractive error measurement Closing remarks Conference Closes

9


Monday 19th July 2004, 11.15 am Chew Sek-jin Memorial Lecture Why Myopia? Clues from Pharmacology Richard A. Stone, M.D. Department of Ophthalmology, Scheie Eye Institute University of Pennsylvania School of Medicine, Philadelphia, PA USA Despite much research, the causes of myopia are poorly understood. The evolving pharmacology of experimental myopia provides novel perspectives potentially relevant to myopia pathogenesis. Prominent among the developmental responses to locally applied drugs, overall eye shape and not only axial length seems regulated by pharmacologic mechanisms. As a clinically accessible parameter, ocular shape may therefore provide a novel and mechanistically informative means to sub-classify ametropia. In parallel with a plethora of data in the general pharmacology and toxicology literature, drugs may exert complex and non-monotonic influences on refractive development. The patterns of these responses suggest that complex modeling might be a useful direction for clinical risk factor analysis and that myopia might productively be conceptualized as a physiologically inappropriate phenomenon rather than as a compensatory response. Finally, the receptor classes now implicated in myopia point to pathogenic mechanisms that have diverse temporal response characteristics, varying between hours-to-days and seconds-or-less. The evidence in different species for conservation of many of the pharmacologic mechanisms regulating eye growth underscores the potential relevance of laboratory findings for understanding clinical ametropia.

10


Monday 19th July 2004, 2.00pm

Keynote Address:

Myopia: pathways to therapy

Professor Bernard Gilmartin Aston University, Birmingham, UK

Myopia is invariably a lifelong condition characterised by high prevalence, significant risk in terms of associated ocular pathology, substantial economic and social burden and, paradoxically, little immediate prospect of remediation, other than by successive refractive correction. Future prospects are, however, encouraging: the last decade has witnessed convergence of myopia research in disciplines such as molecular biology, biomaterials, genetics, wave front optical analysis and information technology. Pharmaceutical, optical and microsurgical treatment modalities for myopia thought improbable just a decade ago are now seen as likely and feasible options for future clinical management. A synopsis will be presented of recent work which has set out pathways to myopia therapy. Recent large-scale studies on children confirm that the major structural correlate of myopia is longitudinal elongation of the posterior vitreous chamber and that, in the developing eye, this is the principal precursor to subsequent compensatory changes in the architecture of the globe. It is now evident that other biometric parameters need to be considered: the profile of lenticular and corneal power; the relationship between longitudinal and transverse vitreous chamber dimensions and the significance of eye shape and ocular volume. The predictive value of cross correlations between these parameters have potential value in exposing a propensity to myopia although refraction at age 5 years-of-age and family history still remain potent predictors. Much recent progress has been made on the genetic characteristics of high myopia (i.e. >6D). Several specific chromosomes have been identified and the application of genetic modeling to large sample monozygotic and dizygotic twin cohorts have computed heritability indices of over 80% for refractive error. The predominance of heredity does not, however, preclude the need to understand further the subtle and complex integration of psychophysiological and optical responses to well-documented environmental triggers such as sustained near work. Recent large scale clinical trials on children have reported on the potential efficacy of optical (i.e. progressive addition spectacle lenses) and pharmaceutical (i.e. topical muscarinic antagonists) modes of treatment. The results, although equivocal, highlight the need to understand further the aetiological significance in humans of retinal image quality and accommodative accuracy. In this regard the correlation between wave front aberration analysis of image quality and visual performance may provide special insight into the genesis, development and subsequent treatment of myopia

11


Accommodative lag at the onset of myopia in children Karla Zadnik, G. Lynn Mitchell, Lisa A. Jones, John R. Hayes, Melvin L. Moeschberger, Donald O. Mutti, College of Optometry, The Ohio State University, Columbus, Ohio, USA. Purpose. We have shown that while prevalent myopes have increased accommodative lag, greater lag was not associated with any increased risk of developing myopia. If increased lag accompanies but does not precede the onset of myopia, when does accommodative lag become different in children who develop myopia? Methods. The age of onset of myopia (at least -0.75 D in each meridian) was identified in 524 children between 6 and 15 years. Accommodative lag to a 4.00-D stimulus measured annually before and after the onset of myopia was compared to age-matched predicted values of lag from 95 children who were always between -0.25 D and +1.00 D in both meridians. Results. Mean accommodative lag for children who became myopic was not significantly different from those who remained emmetropic one year prior to and at myopia onset (mean differences = 0.068 D and 0.026 D; P = 0.16 and 0.35). Lag was significantly higher in children who became myopic compared to those who remained emmetropic one year following the onset by 0.12 D (P <0.001). For the 31.5% of myopes wearing a correction at the onset visit, lag was significantly higher than for emmetropes by 0.22 D (P <0.001). For the 68.5% without correction, lag was slightly less than for emmetropes by –0.06 D (P = 0.03). Conclusions. Increased accommodative lag in myopes compared to emmetropes can be detected at the year of onset of myopia if a child wears a correction. As the majority of children do not wear a correction until one year after onset, increased accommodative lag for myopes as a group is not seen until one year after onset. Lack of differences in lag prior to onset makes it unlikely that accommodative lag will be a useful predictive factor for the onset of myopia.

Effect of cognition and refractive error on oculomotor and cardiovascular function Leon N. Davies, James S. Wolffsohn, Bernard Gilmartin. Neurosciences Research Institute, Aston University, Birmingham, UK. Purpose: To assess objectively and non-invasively autonomic control of accommodation. Methods: Eight emmetropes (EMM), 8 late-onset myopes (LOM) aged 18 to 34 years (mean:22.6+/-4.4years) monocularly viewed stationary numerical digits (at 0.0D and 3.0D) and performed a 2-AFC paradigm. Cognitive demand was varied by altering the speed of presentation and correct response scores for a range of speeds were calculated. The response scores identified five cognitive levels of increasing difficulty for each subject to be employed in a random order. Five 20s continuous objective recordings of the accommodative response measured with the Shin-Nippon SRW-5000 were obtained for each cognitive level, while simultaneous continuous measurement of heart rate was recorded with a piezo-electric pulse transducer for 5 min. Fast Fourier transformation of cardiovascular function allowed the relative power of the autonomic components to be assessed. Results: Increasing the cognitive demand led to a significant reduction in the accommodative response (0.0D: by 0.35+/-0.33D; 3.0D: by 0.31+/-0.40D, p<0.0005). The lag was clinically greater (p=0.07) for LOMs compared to EMMs at both distance (by 0.38+/-0.35D) and near (0.14+/-0.42D). Mean heart period showed a significant reduction with increasing levels of workload (p<0.0005). LOMs exhibit a relative elevation of the sympathetic system activity compared to EMMs. Within refractive groups, however, accommodative shifts with increasing cognition correlated with the parasympathetic activity (r=0.99, p<0.001), but not the sympathetic activity (r=0.62, p>0.05). Conclusions: The significant reduction in accommodative response with increasing cognitive demand is attributable to a concurrent reduction in the relative power of the systemic parasympathetic nervous system. The disparity and accuracy of accommodative response between refractive groups, however, appears to be augmented by changes in the sympathetic nervous system. The findings suggest that concomitant measures of cardiovascular function can provide systematic monitoring of the effect of cognition on accommodative response.

12


Behavioral characteristics of accommodation during periods of sustained reading Elise N. Harb, Frank Thorn, David Troilo New England College of Optometry, Boston, MA, USA. Purpose: The relationship between near work (particularly reading), accommodation, retinal defocus, and the development of refractive state is the subject of much speculation. For example, it has been suggested that inaccurate accommodation, and the associated hyperopic lag, might be a risk factor in the development of myopia. While much is know about the accommodative response under tightly defined experimental conditions, the ethology of accommodation under more natural conditions has been far less studied. We quantified various characteristics of accommodative behavior during a sustained period of near reading under close-to-natural viewing conditions in myopes and emmetropes. Methods: Twenty young adults with stable refractions ranging from +1 D to –7 D were tested with full correction. Accommodation was measured continuously with an infrared optometer (PowerRefractor, Multi-channel Systems) during 10 minutes of sustained reading at several distances. Accommodative amplitude, stimulus lags, and response variability, including power spectrum analysis, were quantified at each of the reading demands. Results: Accommodative behavior was highly variable between subjects in all of the behaviors measured. Within subjects, accommodative lags significantly increased with closer reading distances (Mean lag: 0.71D at 1.5D, 0.93D at 2.5D, 1.00D at 3.5D;repeated measures ANOVA p<0.05), however there was no significant relationship between lag and refractive state. The variability in the accommodative response significantly increased with closer reading distances (Mean s.d.: 0.15D at 1.5D, 0.20D at 2.5D, 0.30 at 3.5D; repeated measures ANOVA p<0.01) and there was a significant increase with increasing myopia (ANOVAs p<0.05). Power spectrum analysis of the accommodative response showed that the power of the microfluctuations increased with closer reading distances (repeated measures ANOVAs p<0.05) and was greater in subjects with increasing myopia at the 3.5D demand (ANOVAs p<0.05). Conclusions: Increased lags and the variability in accommodation at higher accommodative demands suggest that an increase in overall blur at closer reading distances might be related to the development of refractive state. Further study in subjects with progressing refractive errors is required to determine if such behaviors are risk factors for the development of myopia. Supported by NIH EY11228.

Ametropia and ocular biometry in a UK undergraduate population Nicola Logan1, Leon N. Davies1, Alexandra Benavente Perez1, Edward Mallen2, Bernard Gilmartin1, 1 Neurosciences Research Institute, Aston University, Birmingham, UK. 2 Department of Optometry, University of Bradford, Bradford, UK. Purpose: The prevalence of myopia is known to vary both between and within populations with ethnicity and level of education as two the main factors associated with myopia; a higher prevalence of myopia has been reported in university populations compared to a general population and in Far East populations compared to European. There is no current UK database on epidemiology of ametropia and data on myopia prevalence is often extrapolated from USA and Scandinavian studies. Differences in cultural diversity within the UK may reflect a difference in prevalence of myopia. This study investigates the prevalence of myopia in a UK university population and its variation with ethnicity. Methods: A sample of 263 university students was randomly selected. Measurements of refractive error were obtained with an open-field IR autorefractor (Shin-Nippon). Axial length, corneal curvature and anterior chamber depth were measured with an IOLMaster (Zeiss), which uses partial coherence interferometry. Results: The prevalence of myopia (<-0.50D) in the sample was 42.2%, (age range 17 to 30 years). For right eyes, the mean refractive error (spherical equivalent) was -1.10D (SD 2.27), range +3.62 to -9.23D. High myopia (<-6D) was found in 5.2% of the sample. The ethnic variation was white 37.5%, Asian 59.2%, Chinese 2.3% and black 1%. For prevalence of myopia, there was no statistically significant difference with ethnicity in the two main races (white 47%, Asian 52%, p=0.07), however a statistically significant difference was found with gender (females 44.5%, males 36.1%, p<0.05). Axial length correlated with refractive error for both whites (r2=0.59) and Asians (r2=0.66). There were no significant differences between whites and Asians for ocular components. Conclusions: The results are in agreement with Scandinavian studies on myopia prevalence in student populations. In contrary to previous findings the prevalence of myopia in Asian students was similar to that in white students.

13


Instrument myopia during microscopy and factors affecting it Patrick WK Ting1,2,Katrina L Schmid2, Marion E Edwards1*, Carly SY Lam1 1. Centre for Myopia Research, Department of Optometry and Radiography, The Hong Kong Polytechnic University, Hong Kong. 2. School of Optometry, Queensland University of Technology, Brisbane, Australia. * retired Purpose: Instrument myopia (IM) is the over accommodation that occurs when looking through an optical instrument. Past studies using subjective measurement methods report that the magnitude of IM is typically –1.50 D to –2.00 D, with some values as high as –5.00 D. Our aims were to objectively measure the amount of IM that occurs during microscopy and study factors affecting it (i.e. changes in microscope settings and viewing conditions). Methods: An infrared photorefractor (PowerRefractor) was used to objectively measure the amount of IM during the microscopy task. The level of IM of 20 inexperienced (age=24.1±2.9 yr) and nine experienced microscopists (age=31.2±2.9 yr) were measured. The microscope was a binocular light microscope and the exit pupil was 1.25mm. The effect of changing eyepiece power (positive and negative), change in magnification (100x to 400x), target quality (good and poor preparations), illumination of the target (840cd/m2 to 20cd/m2) and form of correction (contact lenses to spectacles) were assessed. Subjects were instructed to fixate and maintain clear view of the cells on the slide while their refractions were measured. Results: IM was greater in inexperienced subjects compared with experienced microscopists (1.03±0.91 D cf 0.43±0.75 D, two way ANCOVA, F1,26=4.707, p=0.039). There was no significant difference in the amount of instrument myopia measured under the different viewing conditions and with changed microscope settings (Repeated measures ANOVA, F6,108=0.938, p=0.4711). There was no correlation between the subjects’ age and refractive error and the amount of IM observed (age r=0.244, p=0.3; refractive error r = −0.311, p=0.182). Conclusion: While the level of IM for a given subject was robust and not affected by changing the task, that the level of IM was less in experienced compared to inexperienced microscopists suggests that the level of IM can be modified. Acknowledgement The work described in this paper was supported by the Research Grants (Project No. A352) of the Area of Strategic Development Fund, The Hong Kong Polytechnic University and QUT International Doctoral Scholarship.

Autonomic correlates of oculomotor and cardiovascular function in myopic subjects Leon N. Davies, James S. Wolffsohn, Bernard Gilmartin, Neurosciences Research Institute, Aston University, Birmingham, UK. Purpose: Quantification of the autonomic nervous system in myopia studies is currently a protracted procedure requiring the use of pharmacological drugs. This study utilises non-invasive Fast Fourier Transformations (FFTs) of heart rate variability (HRV) to investigate the within-task autonomic profile to accommodative stimuli between refractive groups. Methods: Forty functionally emmetropic subjects (10 hypermetropes, 10 emmetropes, 10 early-onset myopes and 10 late-onset myopes) monocularly viewed a stationary high contrast Maltese cross at 0, 1, 2, 3, 4 and 6D accommodative demand. Tonic accommodation (TA) was measured with the aid of a difference of Gaussian target. Five 20s continuous objective recordings of the accommodative response were obtained for each accommodative level with the open-view Shin-Nippon SRW-5000 infrared optometer, while simultaneous continuous measurement of heart period was recorded with a piezo-electric finger pulse transducer for 5 minutes. Results: The relationship between mean heart period, TA and accommodative response (AR) indicated that those subjects with a faster heart rate have a higher TA value (r=-0.56, p=0.011) and a greater AR (r=-0.22, p=0.026). Fast Fourier analysis of HRV shows that increasing the accommodative demand leads to a systematic increase in systemic sympathetic innervation and a concurrent reduction in systemic parasympathetic control in all subjects. Comparing refractive groups, however, illustrates an increase in sympathetic innervation over accommodative levels in late-onset myopes compared to hypermetropes and emmetropes. Conclusions: The data demonstrate covariation between the ocular accommodative response and the prevailing systemic autonomic profile which is modulated by changes in cardiovascular function. The findings suggest that the individual differences observed in TA and steady-state accommodation between refractive groups are, in part, related to subjects’ autonomic profiles and can be quantified using FFT of HRV. Acknowledgements: LND is supported by an EPSRC and BAe Systems CASE award.

14


Spherical aberration and accommodative response in myopes and emmetropes Hema Radhakrishnan, Baskar Theagarayan, Peter M Allen, Daniel J. O’Leary Department of Optometry and Ophthalmic Dispensing, APU and Vision CRC, UNSW, Sydney Australia. Purpose: To determine the effect of ocular spherical aberration on accommodative response in myopes and emmetropes. Methods: In the first experiment, Ocular spherical aberration (SA) and accommodative response to negative lenses and to altering distance were measured in 22 subjects (age: 20 - 24 years). In a second group of subjects, ocular SA was altered by applying aspheric soft contact lenses with known amounts of SA. Accommodative response to negative lenses and to altering distance was measured immediately after altering the SA of the eye and then following 30 minutes of adaptation to the aberrations. Results: In experiment 1 the myopic group was found to have a significantly lower AR to negative lenses when compared to emmetropes and the accommodative response gradient was significantly correlated with the SA of the eye. Subjects with negative ocular spherical aberration were found to be accommodating more accurately than those with positive spherical aberration. Experiment 2 showed that positive spherical aberration increases the lag of accommodation and negative spherical aberration reduces the lag of accommodation in both myopes and emmetropes. Conclusion: Accuracy of accommodative response in myopes and emmetropes is dependent on the ocular spherical aberration. Accommodative response improves on inducing negative spherical aberration and reduces on inducing positive spherical aberration. The change in accommodative response is dependent on the magnitude of induced spherical aberration.

Accommodation dysfunction and myopia progression in young adults Peter M.Allen1,2, Daniel J. O’Leary1,2. Department of Optometry and Ophthalmic Dispensing, APU, Cambridge, UK 2 Vision Co-operative Research Centre, University of New South Wales, Sydney, Australia. 1

Purpose: To see if anomalies in accommodative functions are associated with the progression of myopia. Methods: The following accommodative functions were measured on 64 young adult subjects (30 myopes and 34 emmetropes, with a mean age of 20.14 + 1.55 years); amplitude of accommodation, measured with a modified push-up method, monocular and binocular accommodative facility at 6m using plano/-2.00 D flippers and at 40cm using +2.00/-2.00 D flippers, monocular and binocular accommodative response to target distance (6m, 3m, 1m, 0.5m, 0.4m, 0.33m), AC/A ratio, CA/C ratio, tonic accommodation (dark focus and pinhole), accommodative hysteresis and near-work induced transient myopia. The PowerRefractor was used to measure accommodative responses. The cycloplegic refractive error was measured at the start of the study and 12 months later. Results: Multiple regression analysis was carried out including all accommodative factors associated with myopia progression with p < 0.25. As the most explanatory model of the outcome variable (progression of myopia) using the least number of variables was required, variables were removed starting with the least significant till all variables remaining in the model were significant at p < 0.05. The multiple regression equation was constructed from the unstandardised coefficient values. As there were high levels of colinearity for several of the measures of accommodative facility and also for response-curve measures, the model was constructed using the best predictor from each group. Our predictive model (R2 = 0.29) is: Myopia progression = 0.02*near monocular accommodative facility – 0.35*binocular lag of accommodation at 33cm – 0.45. Conclusions: Two accommodation factors, lag of accommodation at 33cm and accommodation facility, can predict 29% of myopia progression in the young adult subjects.

15


Keynote Address: Animal Models and Human Refractive Errors Earl L. Smith III. College of Optometry, University of Houston, Houston, Texas, USA, Vision Co-operative Research Centre, University of New South Wales, Sydney, Australia. Soon after birth, most infants develop near emmetropic refractive errors, which are then maintained in both eyes throughout childhood and into early adult life. However, for reasons not currently understood, a significant and increasing proportion of the population develop abnormal refractive errors. Literally for centuries scientists and clinicians have debated the question of whether these refractive errors are conditions of genetic origin or whether these errors are a functional adaptation molded by visual experience. Until relatively recently, the weight of scientific evidence supported the idea that refractive errors predominantly reflect non-visual, preprogrammed genetic factors, i.e., an individual’s refractive status was determined by his or her genetic makeup. However, beginning with Wiesel and Raviola’s (1977) report of extreme myopia in form-deprived monkeys, research involving a variety of animal species has clearly demonstrated that visual experience can have a profound effect on ocular growth and the eye’s refractive state. In particular, in many animals, including higher primates, emmetropization has been shown to be an active process that is regulated by optical defocus associated with the eye’s effective refractive state. This substantial body of knowledge strongly suggests that spectacle lenses should influence the ocular development of human children. However, to date there is little direct evidence that spectacle lenses can influence either ocular growth or the refractive status of human eyes. This presentation will highlight the similarities and differences in the optical performance properties of the emmetropization process in animals that are commonly employed in refractive error research and will examine a number of possible explanations for the absence of robust evidence from humans that supports the idea that spectacle lenses, by altering the eye’s effective refractive error, can predictably alter human refractive development.

16


Form deprivation myopia in juvenile and adult rhesus monkeys (Macaca mulatta) Dolores V. Bradley1, Earl L. Smith2, Alcides Fernandes3 1 Yerkes Research Center of Emory University and Spelman College, Atlanta, GA, USA. 2College of Optometry, University of Houston, Texas, USA, and Vision CRC UNSW, Sydney, Australia. 3Division of Visual Science, Yerkes Research Center, Emory University, Atlanta, GA, USA. Purpose. To explore the degree of myopic shift induced in juvenile and adult monkeys with a prolonged period of form deprivation. Methods. Unilateral form deprivation was produced by surgically fusing the eyelid of one eye in each of two juvenile (mean = 1.5 yrs) and two adult (mean = 5.3 yrs) rhesus macaques, at ages corresponding to human ages of approximately 6 yrs and 21 yrs, respectively. Refractive status was measured via cycloplegic retinoscopy and axial length was measured via A-scan ultrasonography. Results. Pre-suture, the juvenile monkeys (mean refractive status (RS) = +1.38 D; mean vitreous chamber depth (VCD) = 11 mm) and the adult monkeys (mean RS = + 1.50 D, mean VCD = 12 mm) were isometropic with similar axial dimensions of the two eyes. Following 126 wks of form deprivation all monkeys exhibited a myopic shift, with some overlap between groups in terms of the absolute RS of the newly opened eyes (juvenile = -1.63 D, -4.5 D; adult = -0.88 D, -2.25 D). The degree of anisometropia, however, was slightly higher for the juvenile monkeys (-2.88 D, -5.5 D) compared to the adult monkeys (-2.26 D, -2.63 D). A similar trend was observed for VCD with juvenile monkeys exhibiting a greater difference between the sutured eye and the fellow eye (0.6 mm, 1.6 mm) compared to adult monkeys (0.3 mm, 0.3 mm). After 64 wks of normal vision, the juvenile group exhibited reductions of anisometropia (0.37 D, 3.75 D) and VCD interocular differences (0.3 mm, 0.9 mm). Conclusions. Consistent with our earlier report, these results demonstrate that vision dependent mechanisms can influence refractive status of primates beyond the postnatal period of development (Smith et al., 1999). These data may also suggest larger effects on interocular differences with an earlier age of onset (Bradley and Fernandes, 2000). References: Bradley DV and Fernandes A (2000). Proceedings of the VIII International Conference on Myopia, Boston MA, July 2000. Smith, EL III, Bradley DV, Fernandes A, and Boothe RG (1999). Optometry and Vision Science, 76(6), 428-432.

The effect of plus lenses on the visual guidance of axial elongation and refractive state in tree shrews Thomas T. Norton, John T. Siegwart, Jr., Angela O. Amedo Department of Physiological Optics, University of Alabama at Birmingham, Birmingham, AL, USA. Purpose: In chicks, plus lenses slow axial elongation and produce a hyperopic eye. We used three approaches to examine the effect of plus lenses in tree shrews with, and without, control of the viewing distance. Methods: Exp.1) at 24 days of visual experience (VE) animals began 11 days wearing binocular -5D, -3D, plano, +3D or +5D lenses. Exp. 2) after 11 days of monocular -5D lens wear, the lens was replaced with: no lens, a -2D lens or a +2D lens. Exp. 3) at 24 days of VE animals began 11 days wearing a monocular -5D lens. Daily, while restrained (45 min) so all objects were >1 m away, the lens was replaced with -5D, -3D, plano, +3D, +4D, +5D, +6D or +10D lens. Results: 1) Binocular plus lenses: most animals did not change their refractive state; a few became slightly hyperopic. 2) During recovery, the no-lens eyes returned to match their fellow control eye. -2D lens-wearing eyes recovered to match the control eye while wearing the lens. +2D lens-wearing eyes recovered to be -2D while wearing the lens (they did not “overshoot” and compensate for the +2D lens). 3) a plano lens for 45 min, while restrained, consistently blocked any myopia from developing in response to the -5D lens worn the rest of the day. In contrast, plus lenses produced highly variable results ranging from complete compensation to the -5 D lens to completely blocking the development of myopia. On average, plus lenses only partially blocked the development of myopia. Conclusions: Rather than fully compensating, eyes tend to stabilize at a residual myopic refractive state while wearing binocular plus-power lenses. This suggests that, in normal eyes, guidance of emmetropization from a myopic refractive state (binocular plus lenses) is much less efficient than emmetropization from a hyperopic refractive state (binocular minus lenses). During recovery from an induced myopia, without control of viewing distance, low-power plus lenses are little different from no lens; they do not cause the recovery to “overshoot”. With viewing distance controlled, wearing a plano lens for 45 min consistently and completely counteracts the myopiagenic effect of −5 D lens worn the rest of the day. In contrast, plus lenses (myopic defocus) inconsistently and on average, only partially counteract the myopiagenic effect of −5 D lens. These data suggest that focused images are a stronger and more consistent “stop” stimulus than myopic defocus.

17


Long term blur adaptation measured from visual evoked potentials John A. Potter, David Troilo, New England College of Optometry, Boston, MA, USA. Purpose: It is well know that human visual performance is significantly decreased by defocus. However, some reports suggest that after prolonged periods of defocus, visual performance may actually improve presumably through a mechanism of blur adaptation. Such adaptation to blur may also have the potential to alter the response characteristics of visual feedback for the control of eye growth and refraction. In this study we used visual evoked potentials (VEPs) to determine whether long term neural adaptation is occurring to imposed blur from defocusing lenses. A gradual increase in VEP amplitude during the defocus period indicates that blur adaptation has occurred. Methods: Following cycloplegia, subjects were corrected for the working distance and then defocused with an additional 1.50 D lens. Stimuli were generated by a Power Macintosh G4 computer and viewed binocularly at a distance of 114cm. Checkerboard stimuli (5 and 0.5 c/deg) subtended a visual angle of 14Â° with the outer 0.5Â° fading to 0% contrast to a luminance of 190cd/m2. VEP amplitudes using the Freiburg EP2000 program were measured before, and at 0, 1, 2, 4, 8, 16 and 32 minutes during, and after imposed defocus. Subjects were instructed to view in the distance in between VEP measures. VEP signals were band-pass filtered, amplified and analyzed off-line. Results: As expected, subjects showed a significant decrease in VEP amplitudes immediately after defocus is imposed. Throughout the defocus period, a slow gradual increase in VEP amplitude was observed. When defocus was removed, amplitudes returned to near baseline levels. Conclusions: The increase in VEP amplitude, in the presence of defocus, indicates that blur adaptation in the primary visual system does occur in response to the defocus. These results support the findings from earlier studies and may further our understanding of the neural mechanisms influencing emmetropisation and myopia development.

18


Keynote address: Temporal and spatial aspects of visual guidance of eye growth Josh Wallman, Department of Biology, City College, City University of New York The eyes of birds, rodents and primates are under homeostatic control in which the sign of blur (myopic vs. hyperopic) determines eye growth. This is shown by the fact that imposing blur of either sign with spectacle lenses results in eye-growth that reduces the blur. If this control acts during normal life it must cope with the fluctuating magnitude and sign of blur that the eye experiences as it looks about. Recent evidence shows that the different compensatory responses of the eye have different temporal characteristics. These differences might explain why that brief periods of myopic defocus can cancel long periods of hyperopic defocus in several species. This in turn may help explain why even though people who do much nearwork are more likely to be myopic than those who do little near-work, the degree of myopia is poorly predicted by the hours of near-work. Another important factor, overlooked until recently, is the spatial distribution of refractive error across the retina. In birds, it is clear that separate regions of the eye can adjust their refractive error somewhat independently; in mammals, the refractive status of different regions may collectively determine the growth of the eye. Consequently, in humans, myopic progression may be driven more by hyperopia in the peripheral retina than by myopia at the fovea.

19


Wave aberrations in rhesus monkeys recovering from vision-induced ametropias Ramkumar Ramamirtham, Chea-Su Kee, Ying Qiao-Grider, Li-Fang Hung, Austin Roorda, Earl L. Smith, College of Optometry, Houston, Texas, USA and Vision Co-operative Research Centre, University of New South Wales, Sydney, Australia. Purpose: Abnormal visual experience imposed by spectacle lenses or optical diffusers has been shown to alter the refractive status and higher order aberrations in infant rhesus monkeys. It is known that restoring unrestricted clear vision in these animals allows their eyes to emmetropize. However, it is not known whether restoring unrestricted clear vision also results in a recovery to normal amounts of wave aberrations. Hence the purpose of this study was to compare wave aberrations between normally reared monkeys and monkeys that were recovering from abnormal visual experience in early life. Methods: Our subjects were 5 normal infant monkeys (control group) and 10 monkeys in which unrestricted clear vision was restored following altered visual experience early in life (recovery group). Abnormal visual experience in both eyes was produced either with diffusers or spherical spectacle lenses from 3 to 20 weeks of age. The eye’s aberrations were measured periodically (central 5 mm pupil) using a Shack-Hartmann wavefront analyzer until 42 weeks of age. To facilitate these measurements, the animals were anesthetized and cyclopleged. Results: At the end of the treatment period, the average RMS error for the monkeys that had abnormal visual experience (0.29 m +/- 0.09) was significantly greater (p=0.018) than in the normal monkeys (0.19 µm +/- 0.04). However 22 weeks after restoring unrestricted clear vision, there was no significant difference (p=0.65) in average RMS error between the normal (0.21 µm +/- 0.07) and the recovery groups (0.23 µm +/- 0.07). Conclusion: Monkeys with higher amounts of wave aberrations due to abnormal visual experience in early life recover to normal amounts of aberrations after unrestricted vision is restored, i.e, the structural changes responsible for higher aberration are not permanent. Similar to spherical and astigmatic errors, the higher order aberrations are influenced by vision-dependant mechanisms.

High order wave aberration of chicks due to constant light rearing and its recovery Howard C. Howland1, Tong Li1, Yoko Hirohara2, Toshifumi Mihashi2, 1 Neurobiology and Behavior, Cornell University, Ithaca, NY, USA. 2 Topcon Corp., Tokyo, Japan. Purpose: Our previous studies showed that under constant light (CL), chicks developed progressive hyperopia, optical aberrations and other ocular abnormal dimensions. Chicks can recover from hyperopic refractions in a week. We wished to determine if the high order optical aberrations (HOA) of CL chicken eyes recover as quickly as does refraction. Methods: Three groups of 6 chicks (Gallus Gallus domesticus) were raised either in a normal diurnal light cycle (12/12, one group) or under light conditions (two groups) for first 25 days of their life. At day 25, the refractions and wavefront aberrations and other ocular components were determined. Then, one group of CL chicken was switched to a 12L/12D rearing condition. Further measurements were performed 5, 10 and 29 days after switching. HOA were analyzed using Zernike polynomials up to 6th order and the pupil sizes measured simultaneously. Results: While hyperopic refractions of CL chicks recovered from 16.2 diopters to 5.33 diopters in 10 days, the same as in normal controls, HOA remained almost the same, from 0.836 microns rms for 3.5 mm pupils to 0.858 microns RMS for 4.0 mm pupils. The radii of corneal curvatures (RCC) of recovery chicks also remained larger. Although the HOA of CL chicks decreased, a similar decrease in HOA was observed in normal chicks as well. Conclusions: Our results show that the high order aberrations due to the CL treatment do not recover as quickly and completely as the refractions, and that abnormal corneal shapes under CL conditions may be responsible for the increased high order aberrations in CL reared chicks. Supported by NIH Grant EYO2994 to HCH. References: Li, T., Troilo D., Glasser, A. and Howland, H.C. (1995). Vision Res. 35(9):1203-1209. Li, T. and H.C. Howland (2000) Vision Res. 40 (17): 2249-2256. Li, T. Troilo, D. & Howland, H.C.(2000) Vis. Res. 40(18):2387-2393. Li, T. & Howland, H.C. (2003). IOVS 44(8): 3692-3697.

20


Failure of limited proteolysis of pigment epithelium-derived factor (PEDF) in Tenon’s capsule of children with progressive myopia Elena N. Iomdina1, Alexandra V. Lazuk1, Irina A. Kostanyan2, Sergei S. Zhokhov2, 1 Laboratory of Myopic Studies, Moscow Helmholtz Research Institute of Eye Diseases, Moscow, Russia. 2 Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, RAS, Moscow, Russia. Purpose: to compare PEDF content in Tenon’s capsules of patients with progressive myopia and hyperopia. Materials and Methods: Tenon’s capsule samples were obtained from 20 patients aged 6-14 (10 with myopia -4.5 to -10.0 D and 10 with hyperopia +0.5 to +4.0 D) during scleroplasty and surgeries for squint. PEDF content was determined in sample homogenates by Western blot analysis using polyclonal antibodies against PEDF molecule fragment 345Lys-366Glu. Results. In all samples, a band corresponding to the full-length PEDF molecule (~50 kDa) was detected. Its average intensity was slightly less in hyperopic patients. In nearly all samples of hyperopic patients another band (~45 kDa) was also revealed. This band was detectable only in 3 of 10 myopic patients, its intensity was much weaker than in most cases of hyperopia. Conclusions. A limited proteolysis of PEDF occurs in Tenon’s capsule of patients with hyperopia, which is probably suppressed upon myopia. The only bond 382Leu-383Thr appears to be hydrolyzed, which was shown to be the primary target of serine proteases. Its cleavage changes the scope of PEDF activities (5). Our observations validate the usage of Tenon’s capsule as an object of myopia pathogenesis studies during lifetime and justify further investigations in this field. References: Trier K., Olsen E.B. et al. (1999). Br. J. Ophthalmol., 83, 1370-1375. Jablonski M., Tombran-Tink J. et al (2000). J. Neurosci., Vol. 20, p. 7149-7157. Yasui N., Mori T. et al (2003). Biochemistry, Vol. 42, p. 3160-3167. Shauly Y, Miller B. et al (1992). Invest. Ophthalmol. Vis Sci, 33, 651-656. Kostanyan I.A., Zhokhov S.S. et al. (2000). Russian Journal of Bioorganic Chemistry (Moscow), Vol. 26, 505-511. (In Russian).

The effects of GABA-B and GABA-C antagonists on myopia development in chick. Katrina L. Schmid1, D. R. Brinkworth1,K. M. Wallace1, R. E. Payor2, C. Fritsch2, G. N. Lambrou2 1 School of Optometry, Queensland University of Technology, Brisbane, Queensland, Australia. 2 Disease Area Ophthalmology, Novartis Institutes for BioMedical Research, Basel, Switzerland. Purpose: It is suggested that GABA-B and GABA-C antagonists are effective at inhibiting myopia in chick (Stone et al., 2003). We examined this further using lens-induced myopia (LIM) and a range of GABA compounds. Methods: RhodeIslandRed-RhodeIslandWhite cross chicks (n=7-11 per group) were monocularly fitted with -15D lenses on post-hatch day 8. Daily intravitreal injections (10Î¼l) containing a GABAergic agent or dH2O were given to lens wearing eyes. Compounds included i) GABA-B antagonists CGP56433A (55pmoles, 11 and 55 nmoles), CGP56999A (1.4pmoles, 0.28 and 1.4 nmoles), CGP61334 (28pmoles, 28nmoles), CGP62349 (1.4pmoles, 1.4nmoles), and CGP63360A (17pmoles, 17nmoles), ii) GABA-B/C antagonist CGP36742 (0.28, 56, 140, 280 and 560 nmoles, 1.77Î¼moles), and iii) GABA-C antagonist TPMPA (3.5pmoles, 0.35, 3.5, 35, 70 and 350 nmoles, 1Î¼mole). After 4.5 days of treatment refractive errors (RE) and axial length (AL) were measured. All techniques were performed under isoflurane anaesthesia. Results: The GABA-B antagonists slightly exacerbated (CGP61334: 28%) or slightly inhibited LIM (CGP56999A: 39%), and had no effect (CGP61334: 2%) to a slight inhibitory effect on axial elongation (CGP62349: 46%); data were not statistically different from control (dH2O: Diff RE=-11.31D, Diff AL=0.54mm cf GABA-B Diff RE = -14.5D to -6.95D, Diff AL=0.55mm to 0.29mm). The GABA-B/C and GABA-C antagonists had a much greater inhibitory effect. At the third highest dose tested, CGP36742 inhibited 80% of the myopia (RE= -1.60D) and 77% of the axial elongation (AL=0.11mm) (cf dH2O, RE p<0.001, AL p<0.001). TPMPA significantly inhibited LIM at 6 doses; the third highest dose inhibited 81% (RE= -2.20D) of the myopia and 87% (AL=0.07mm) of the axial elongation. Conclusion: Our results suggest that GABA-B antagonists are at best only slightly effective at inhibiting LIM. This finding is in contradiction with previously published data. Our results suggest a greater role for the GABA-C receptor in myopia. This work was funded by Novartis Pharma. References: Stone RA, Liu J, et al. (2003) Invest Ophthalmol Vis Sci, 44, 2933-46.

21


Keynote address: Signalling mechanisms in choroid and sclera Thomas T. Norton, Department of Physiological Optics, University of Alabama at Birmingham, Birmingham, Alabama, USA.

Studies in several species (chick, macaque monkey, marmoset, tree shrew) have suggested that a signalling cascade begins in the retina, passes the RPE into the choroid, and thence regulates the extracellular matrix of the sclera to control axial elongation and refractive state. In three species, amacrine cells appear to be involved with a “stop elongating” signal (Fischer et al., 2001; Zhong et al., 2004; Stell et al., 2004). The pathway through or around the RPE is unknown, although recent studies on changes in the transepithelial potential of the RPE after optic nerve section (Rymer et al., 2004) are suggestive. In the choroid, retinoic acid levels may constitute a signal that regulates the levels of glycosaminoglycans in the sclera (Mertz & Wallman, 2001). Additionally, Rada (Rada et al., 2001) has reported another substance in choroid (ovotransferrin) may modulate scleral remodelling. In the sclera, cartilage grows during myopia development, while the fibrous sclera thins. Both undergo remodelling that leads to either an increased, or decreased rate of axial elongation. Recent studies in tree shrew fibrous sclera show changes in gene expression for structural proteins (collagen [Gentle et al., 2003), degradative enzymes (MMP-2, MT1 MMP), tissue inhibitors of metalloproteinases (TIMP-3) (Siegwart and Norton, 2002; Siegwart et al., 2004) and changes in GAG levels (German et al., 2002) during the development of induced myopia and recovery. These changes result in changes in the biomechanical properties of the fibrous sclera (increased “creep” during myopia development) that appear to regulate the axial elongation rate and control the location of the retina relative to the focal plane. Knowledge of the changes in gene expression that occur in animal models may point toward loci that play a role in the genetics of human myopia. References: Fischer, A. J., McGuire, J. J. et al (1999) Nat. Neurosci., 2, 706-712. Gentle, A., Liu, Y. et al (2003) J. Biol. Chem., 278, 16587-16594. German, A. J., Baker, J. R., & Norton, T. T. (2002) Invest. Ophthalmol. Vis. Sci., 43, EAbstract 215. Mertz, J. R., & Wallman, J. (2000) Exp. Eye Res., 70, 519-527. Rada, J. A., Huang, Y., & Rada, K. G. (2001) Curr. Eye Res., 22, 121-132. Rymer, J. M., Choh, V., & Wildsoet, C. (2004) Invest. Ophthalmol. Vis. Sci., 45, E-Abstract 58. Siegwart, Jr., J. T., & Norton, T. T. (2002). Invest. Ophthalmol. Vis. Sci., 43, 2067-2075. Siegwart, Jr., J. T., Robertson, J. D., & Norton, T. T. (2004). Invest. Ophthalmol. Vis. Sci., 45, E-Abstract 1232. Stell, W. K., Tao, J. et al (2004) Invest. Ophthalmol. Vis. Sci., 45, E-Abstract 1159. Zhong, X., Ge, J., Smith III, E. L., & Stell, W. K. (2004). Invest. Ophthalmol. Vis. Sci., 45, in press.

22


Effect of Hyperbaric Oxygen on Guinea Pig Lens Optical Quality and on the Development of Myopia Jacob G. Sivak1*, Olanrewaju M. Oriowo2,1, Frank J. Giblin3, Victor R. Leverenz3, John R. Trevithick4,1 and Vladimir Bantseev1 1

School of Optometry University of Waterloo, Waterloo ON, Canada; 2Dept. of Optometry/St. Erik's Eye Hospital, Karolinska Institute, Stockholm Sweden; 3Eye Research Institute of Oakland University, Rochester MI, USA; 4 Department of Biochemistry, Faculty of Medicine, University of Western Ontario, London ON, Canada. Purpose: The main objective of this study was to investigate the effect of in vivo hyperbaric oxygen (HBO) treatment of albino guinea pigs on ocular refractive state and optical properties of the lens in vitro, as well as on the integrity of the mitochondria of the lens. Methods: The animals were treated 30-35 times (2.5-3 months) or 70 times (6 months) with HBO. Results: An increased level of lens nuclear light scattering was evident by slit-lamp at 30 treatments, and this increased at 70 treatments. After 30-35 HBO treatments a myopic shift in refractive state of the eye was seen in two separate studies with two different refractionists. Also, the average back vertex distance of the lens was significantly shorter after 35 HBO treatments while spherical aberration (focal variability) increased after 70 treatments. No difference in refractive state was noted after 70 HBO treatments (a reversal of the initial myopic effect). The mitochondrial distribution and morphology of the lens epithelium and the superficial cortical fiber cells were normal after both 35 and 70 HBO treatments, highlighting that HBO treatment does not affect the superficial cortex of the lens. The results of the in vitro lens optical analysis carried out in this study correlate with the myopia observed after 30-35 HBO in vivo treatments. Conclusions: A similar reversible myopia and increase in lens nuclear light scattering is known to occur in humans treated with HBO for extended periods and the results suggest that the myopia was caused by a change in the refractive index of the lens. The significant loss of sharp focus after 70 HBO treatments can be correlated with previous reports of biochemical and morphological changes associated with HBO-induced loss of lens nuclear transparency in mature guinea pigs.

The Longitudinal Orthokeratology Research In Children (LORIC) study in Hong Kong. A pilot study on refractive changes and myopic control Pauline Cho, PhD; Sin Wan Cheung, MPhil; Marion Edwards, PhD Department of Optometry, Hong Kong Polytechnic University, Honk Kong. Purpose: Myopia is a common ocular disorder, and progression of myopia in children is of increasing concern. Modern orthokeratology (ortho-k), is effective for myopic reduction and has been claimed to be effective in slowing the progression of myopia (myopic control) in children, although scientific evidence for this has been lacking. This two-year pilot study was conducted to determine if ortho-k can effectively reduce and control myopia in children. Methods: We monitored the growth of axial length (AL) and vitreous chamber depth (VCD) in 35 children (aged 7-12 years) undergoing ortho-k treatment and compared the rates of change with 35 children wearing single-vision spectacles from an earlier study (control). For the ortho-k subjects, we also determined the changes in corneal curvature and the relationships with changes of refractive errors, AL and VCD. Results: The baseline spherical equivalent refractive errors (SER), the AL and VCD of the ortho-k and control subjects were not statistically different. All the ortho-k subjects found post-ortho-k unaided vision acceptable in the daytime. The residual SER at the end of the study was −0.18 ± 0.69 D and the reduction (less myopic) in SER was 2.09 ± 1.34 D (all values are mean ± SD). At the end of 24 months, the increases in AL were 0.29 ± 0.27 mm and 0.54 ± 0.27 mm for the ortho-k and control groups respectively (unpaired t test; p = 0.012); the increases in VCD were 0.23 ± 0.25 mm and 0.48 ± 0.26 mm for the ortho-k and control groups, respectively (p = 0.005). There was significant initial corneal flattening in the ortho-k group but no significant relationships were found between changes in corneal power and changes in AL and VCD. Conclusions: Ortho-k can have both a corrective and preventive/control effect in childhood myopia. However, there are substantial variations in changes in eye length among children and there is no way to predict the effect for individual subjects.

23


Refractive error and visual acuity changes in orthokeratology patients Sin Wan Cheung, MPhil; Pauline Cho, PhD; Wan Sang Chui, MPhil; George Woo, PhD Department of Optometry, Hong Kong Polytechnic University, Hong Kong. Purpose: To evaluate the refractive error and visual acuity (VA) changes in orthokeratology (ortho-k) subjects and to compare the post-ortho-k VA with the aided VA of spectacle-wearing subjects. Methods: Distance post-ortho-k unaided and aided VA at four different contrast levels of 33 ortho-k subjects and the aided VA of 33 age-, gender- and initial refractive error-matched spectacle-wearing subjects were taken and compared using the Waterloo Four-Contrast LogMAR VA Chart which comprises four charts of different contrast levels (90%, 48%, 21% and 7%). Results: The mean±SD percentage of reduction in spherical equivalent achieved in the current study was 91±13% and 84±14% in the better and the worse eyes respectively. Spherical equivalent was significantly reduced in the ortho-k subjects, with no significant change in the astigmatism. Post-ortho-k unaided VA in the better eye were 0.01±0.11, 0.08±0.11, 0.22±0.12 and 0.47±0.14 with the 90%, 48%, 21% and 7% charts respectively, and were better than those in the worse eye. Post-ortho-k unaided VA was poorer than post-ortho-k aided VA by 0.09 to 0.12 log units because of the significant residual refractive error. Aided VA of the spectacle-wearing subjects was significantly better than post-ortho-k unaided VA of the ortho-k subjects. However, when compared to 18 ortho-k subjects with low residual refractive error, the aided VA of the spectacle-wearing subjects was not different from the post-ortho-k unaided VA of these ortho-k subjects. Conclusions: We found that ortho-k reduced over 80% of spherical equivalent but the post-ortho-k unaided VA could be poorer than the post-ortho-k aided VA up to one line on the logMAR chart. Poor post-ortho-k unaided VA were due to significant residual refractive error. With residual refractive error of ≤±0.50 diopters, the postortho-k unaided VA was as good as the aided VA of the spectacle-wearing subjects.

Vision screening for myopia and other target conditions in South Auckland AIMHI schools Ivan Wood, Department of Optometry and Vision Science, Auckland, New Zealand. Purpose: To determine the prevalence of Myopia and other types of ametropia in economically disadvantaged (decile 1) 13 year old Pacific Island schoolchildren. Methods: Four hundred and twenty five 13 year old Pacific Island children were screened for Myopia and other refractive ametropias using the City University School Screening Program. The screened positives were then received a masked optometric examination. Glasses and or other interventions were prescribed after this Optometric consultation. Results: Eighty -five 85 (20%) children failed the vision screening for one or more of the target conditions i.e. Myopia Hypermetropia Astigmatism. Forty One 41 of these 85 children were unaware of any visual problems. Subsequent Optometric examinations confirmed that 59 (13.8%) required a myopic correction of >=-0.50 Dioptres, with 16 Children (4.2%) presented with significant Hypermetropia (>=+2.50DS.). Preliminary % estimates for myopic error vs ethnicity : Chinese 22% Maori 12%,Samoan=22%,Tongan=11%Cook Island=0.05% So far a 1/5th (19/75) of the children .have received the RX. Most of RXs (80%) required charitable funding Additionally 71 (18.6%) children presented symptomatic NPC/near phorias with 4 (0.1%) present with referable (pathological) condition. Conclusions: This study shows that refractive error is the principal cause of reduced vision in 55% of the positively screened children, with Myopia accounting for 73% of the referred population. Decompensated heterophorias and pathology accounted for the remaining causes of referral. Other studies have shown that the principal cause of reduced vision (6/12 or less) is refractive error in 89.5% to 56% of positively screened children. Strabismus (4%), Amblyopia 5% to 9%, and Ocular disease, account for the remaining causes.

24


A one-year follow-up study of refraction, accommodation and axial length of schoolchildren in the far north region Yury Z. Rosenblum1, Oleg N. Onufriychuk2, 1 Optometry and Ophthalmoergonomics Laboratory, Moscow Helmholtz Research Institute of Eye Diseases, Moscow, Russia. 2 Ophthalmological Department, Kogalym Town Hospital, Kogalym, Khanty-Mansiysk Autonomous District, Russia. It is known that acquired myopia mainly starts at the age between 7 and 14. It would therefore be useful if we could predict the probability of myopia onset at this age. E.S. Avetisov (1-5) established three precursors of myopia (heredity, weakness of accommodation and mechanical pliancy of the sclera). T. Sato (6) and A.I. Dashevsky (7) attach importance to the accommodation spasm. In recent years, a series of papers have been published on the observation of schoolchildren who acquired myopia (8-16). Subjects who later became myopic showed a longer eye axis, reduced accommodation, esophoria and high fusional reserves in near vision. There are indications that myopia develops especially often in schoolchildren living in the regions of Far North (17, 18). Purpose. Estimation of prognostic symptoms of myopia onset in Russian schoolchildren of the Far North region. Methods. 338 children (630 eyes) of the Kogalym secondary school aged 10-14 were examined twice with an interval of one year. The examination includes measuring of 1) refraction for normal pupils and pupils dilated by mydriacyl using an autorefractometer AR 3300 by Nikon; 2) absolute and relative accommodation at 333 mm; 3) the anterior-posterior eye axis using the A-ultrasound device EOM - 24. Results. Over the year, 54 eyes showed a refraction shift toward myopia. A true myopia emerged on 11 eyes. Direct prognostic signs of myopia onset included the elongation of the eye axis to 24 mm or more and the decrease of positive relative accommodation down to 1.0 D. Often enough (18.4%) the pseudomyopia precedes the onset of true myopia. Conclusion. Prognostical features of myopia are: elongation of axial length of the eye to 24 mm or more and the decrease of positive relative accommodation down to 1.0 D References: 1. Avetisov E. S. Myopia. Moscow. Medicina 1999. 285 p. (in Russian) 2. Avetisov E. S. Proc. Intern. Symp. “Myopia”, Moscow, 1989, p. 9-15 3. Avetissow E.S. Klin. Mbl. Augenheilk., 1979. Bd. 175. 5. 735-740 (in German). 4. Avetissow E.S. Klin. Mbl. Augenheilk., 1980. Bd. 176. S. 394-397 (in German). 5. Avetissow E.S. Klin. Mbl. Augenheilk. 1980. Bd. 176. S. 777-781 (in German) 6. Sato T. Kohana Hebarudo Printing Co. Ltd. 1957. 185 p. 7. Dashevsky A.I. Pseudomyopia Moscow, Medicina, 1973. 152 p. (in Russian) 8. Goss D.A., Jackson T.W. Optom. Vis Sci. 1995. v. 72, p. 870-878. 9. Goss D.A., Jackson T.W. Optom. Vis. Sci. 1996, v 73, p. 263-268. 10. Goss D.A., Jackson T.W. Optom. Vis. Sci. 1996 p. 269-278. 11. Goss D.A., Jackson T.W. Optom. Vis. Sci. 1996, v. 73, p 279-282 12. Goss D.A., Jackson T.W. Optom. Vis. Sci. 1999 v 76. p 286- 291. 13. Edwards M.H., Fan Chi Shing. Opt. Vis. Sci. 1999, 76, 272-76 14 Lam S.Y., Edwards M.H. et al. Optom Vis. Sci. 1999, v 76, p. 370-380. 15. Mew May, Wee May, Edwards M. H. Optom. Vis. Sci. 1999, v 76, p 387-392. 16. Edwards M. H., Brown N.B. Ophth. Phys. Opt. 1996, v 16, p. 243-246. 17. Rosenblum Yu. Z. Vestn. Ophthalm., 1984, No. 1, p. 34-39 (in Russian). 18. Makarov P.G., Basarny V.F. Conf. on Pediatric Ophthalmology. Moscow, 1971, p. 88-90 (in Russian).

Psychophysical measurements of blur thresholds in myopes and emmetropes Niall C. Strang1, John A. Potter2, David Whitaker3, 1 Department of Vision Sciences, Glasgow Caledonian UniversityGlasgow Caledonian University, Glasgow, Scotland, UK. 2 New England College of Optometry, Boston, USA. 3 Department of Optometry, University of Bradford, Bradford, UK. Purpose: The amount of optical defocus that is added to an in-focus target before the target is perceived as blurred is thought to be greater in myopic subjects. Greater individual variation has also been reported in myopic children using computer generated blur. However, these differences have only been measured when blur is introduced from an in-focus baseline level. The aim of this study is extend this work to measure computer generated blur thresholds over a range of in-focus and blurred baseline levels. Methods: 12 fully corrected visually normal subjects (6 myopes and 6 emmetropes) with astigmatism of less than 1.00 DC participated in the study. The stimuli consisted of a high contrast cross target (0.0 logMAR equivalent) whose spatial frequency profile was Gaussian blurred using NIH Image. A 2-AFC method of constant stimuli paradigm was used to determine blur thresholds over a range of blurred baseline levels. Subjects were consecutively presented with two cross targets and instructed to identify which cross was more blurred. The more blurred cross was randomly presented from one of seven increasing blur levels. Thresholds were calculated as the 75% correct level using logistical functions applied to the data. Results: No statistical difference was found between the two refractive groups over four baseline blur levels, although a significant interaction between refractive groups and blurred baseline level was found (p < 0.05). Extending the blurred baseline range in six of the original twelve subjects revealed a significant difference between the two refractive groups with increasing baseline blur (p < 0.05). Weber fractions were found to increase (p < 0.05) with increasing myopia, indicating that blur discrimination performance was significantly worse in higher myopia. Conclusions: Myopic subjects were found to have higher Gaussian blur thresholds than emmetropes.

25


Visual acuity and guiding performance in a group of guide dogs: Effect of naturally-occurring myopia Andrew V Collins, John R. Phillips, Poonam Bhana, Nicky Dayton Department of Optometry and Vision Science, The University of Auckland, Auckland, New Zealand. Purpose: To achieve reliable measures of visual acuity using a novel computerised acuity test in a group of guide dogs which exhibit naturally-occurring myopia (Corbett et al, 2002). To examine the relationship between refractive error, visual performance and guiding ability in this group of dogs. Method: Refractive error was measured by cycloplegic retinoscopy in both eyes of 61 dogs (39 Labrador Retrievers) from the RNZFB Guide Dog Centre. Visual acuity was measured in a subset (19 dogs) using a novel computerised acuity test (CAT) which employs dynamically-presented vanishing optotype targets and a preferential-looking paradigm. Measured visual performance was compared with guide dog training scores supplied by the RNZFB Guide Dog Centre. Results: Mean sphere refractions ranged from -3.63D to +2.81D (mean of L and R eyes); mean = +0.28 ± 0.96D (n = 61). No significant astigmatism or anisometropia was found. Myopia of at least -0.50D was measured in 11.5% of dogs. The mean visual acuity for all dogs was logMAR 0.572 ± 0.276 (6/24). The mean visual acuity for the subset of emmetropic dogs was logMAR 0.420 ± 0.125 (6/16), while the group of myopic dogs (myopia greater than -0.50D) exhibited a reduced mean visual acuity of logMAR 0.914 ± 0.215 (6/49). A strong negative correlation (r = -0.993) was found between measured visual acuity and refractive error in the myopic dog group. A comparison of training scores and vision measurements showed no significant effect of visual acuity on the suspicion score. Conclusions: We have developed a novel computerised preferential-looking acuity test and measured visual acuity in a population of guide dogs. A strong relationship was found between the degree of myopia and decreased in visual acuity in these dogs. However, we found no relationship between decreased visual acuity due to myopia and guide dog performance. References: Corbett. R., Donovan, C., Collins, A.V., Phillips, J.R. (2002). Familial trends in refractive error in a group of guide dogs. 9th International Conference on Myopia, Hong Kong. Abstract No. 12.

The state of eye fundus in children and adolescents with congenital myopia Elena P. Tarutta, Laboratory of Myopic Studies, Helmholtz Research Institute of Eye Diseases, Moscow, Russia. Congenital myopia is a special form of refraction which is developing during the intrauterine growth of the foetus. Congenital myopia is diagnosed in 0.1-0.2% of school-age children. In 30% of children with such pathology, low vision is observed. The purpose of this paper was to study the particularities of the state of eye fundus in patients with congenital myopia. Material and methods. 36 eyes with moderate and high myopia were examined in patients aged 2-17. In most cases, the diagnosis was made at an early age, at 1-2 years. 29.8% of the subjects were somatically healthy, whilst 62% had a hereditary burden. Pathologies of the antenatal and intranatal periods were noted in 58% of cases. Results. Eye fundus changes of a congenital nature were noted in 196 eyes (66.2%). We also noted a much earlier onset of dystrophic changes in central and peripheral parts of the eye fundus as compared to acquired myopia. A central chorioretinal dystrophy (CCRD) was revealed in 26 eyes (8.8%), the earliest age of its onset was 9 years. In 5 of these eyes, a neovascular membrane was detected. This is a contrast to early acquired myopia for which CCRD was diagnosed in 1.2%, the earliest age of its onset was 15 years. In so-called school myopia, CCRD never emerged until the age of 19 and in most cases it only appeared in one’s thirties. Peripheral chorioretinal dystrophy in congenial myopia was also revealed earlier in life and with a higher frequency than in early, acquired and school myopia: 46.2%, 28.2% and 31.7%, respectively. Conclusion. In congenital myopia, along with typical congenital changes in the eye fundus, a gradual increase of occurrence and severity of dystrophic changes with age was revealed, which carried a poor visual prognosis.

26


Acoustical Density of the Sclera as a Prognostic Factor of the Clinical Course of Myopia Elena P. Tarutta1, Marina V. Maximova1, Galina V. Kruzhkova2, 1 Laboratory of Myopic Studies, Helmholtz Research Institute of Eye Diseases, Moscow, Russia. 2 Ultrasound Dept., Helmholtz Research Institute of Eye Diseases, Moscow, Russia. Purpose: to estimate the informative value of the in vivo acoustic study of biophysical properties of the sclera for the prognosis of PVCRD development. Material and methods. The acoustic density of the sclera (ADS) was measured by amplitude attenuation of the echosignal [1] from the scleral capsule (the main constituent of the signal from the eye wall) in the equatorial zone. A/B Scan System(Allegran Humphrey) was used. After ADS measurement, 126 eyes of 63 children with progressing myopia aged 9-11 were divided into two groups according to our previous data [2]: (1) with ADS<=39.0dB (unfavorable PVCRD prognosis, 48 eyes) and (2) ADS>39.0 dB (favorable prognosis, 78 eyes). By the time of the first examination the mean R in group 1 was -6.18D and in group 2 it was -5.6D. Respectively, the mean age was 9.5 and 9.7. In all patients, changes in the eye fundus were absent or were only limited to scleral crescents. All patients were followed up for 10 years with regular examinations every 6 months involving thorough ophthalmoscopy of the eye fundus periphery. No sclera strengthening treatment was given. Results. By the end of the follow-up period the mean R in group 1 was -8.5D and in group 2 it was -6.8D. Over 10 years, PVCRDs emerged in 64.6% (31 eyes) of group 1 and in 25.6% (20 eyes) of group 2. Of these, lattice degeneration developed in 33,3% of eyes in group 1 and in 17.9% of group 2. Isolated retinal breaks emerged in 14,6% and 2,6%, respectively, and snow-flake degenerations in 12,5% and 3,8% of eyes. Natural course of PVRCD in the longitudinal cut is considered. Conclusion. Myopia progression in children and adolescents is accompanied by PVCRD development. Studies of acoustic properties of the sclera may help in the prognosis of complicated myopia. References: Parker K.J., Lerner R.M., Waag R.C. (1988). IEEE Trans. Biomed. Eng., 35, 12, 1064-1067. Avetisov E.S., Fridman F.E., et al. (1996). Vestnik Ophthalmologii, 2, 41-43 (In Russian).

Low power lasers in the treatment of low and moderate progressive myopia Elena P. Tarutta1, Alexandra V. Lazuk1, Elena N. Iomdina1, Leonid S. Orbachevsky2, 1 Laboratory of Myopic Studies, Helmholtz Research Institute of Eye Diseases, Moscow, Russia. 2 ZAO Macdel Technologies, Moscow, Russia. From the onset of myopia progression, it is accompanied by accommodative and hemodynamics disorders (E.S.Avetisov, 1999). Purpose: to assess the efficiency and safety of low-power infrared laser radiation impact on accommodation and hemodynamics of myopic eyes. Methods. Over the last 10 years, trans-scleral infrared low energy laser radiation treatment of the ciliary body (wavelength 1.3 mkm, power at scleral level 1.0-1.5 mWt) with MACDEL-09, and stimulation of the sensory system of the eye with the help of a laser speckle structure (He-Ne laser MACDEL-08, wavelength 0.63 mkm, exposition time 3-4 minutes) was administered to patients with myopia of 0.5-5.5D aged 7 or older. Immediate and remote (5-year) treatment results of 487 children (aged 7-13 at the beginning of follow-up period) with an average myopia of 3.3±1.4D are followed. Courses of treatment (10 episodes in 10 days) were given every six months. The control group (80 children in a similar condition) did not receive such treatment. Results. Two weeks after the course showed an average reduction of subjective refraction (optimal correction lens power) by 0.53±0.1D. It was accompanied by an increase of uncorrected visual acuity (averagely, by 0.16±0.08). The positive relative accommodation averagely increased by 1.9 D (1.8 times). The rheographic coefficient grew from 2.1±0.03% to 3.4±0.02%. All parameters tend to drop after 4-6 months and rise again after a repeated course. A reduction in the progression rate (averagely by 1.7 times) is noted in 78% patients for a year and in 64% over the whole observation period. After 5 years, the main group showed the average value of R=-4.8±1.9D and the control group -5.5±1.8D. No complications were noted. Conclusion. The method of low-power laser treatment is easily applicable in out-patient conditions, is well tolerated by children and can be included into the treatment complex for progressive myopia.

27


An inhibitory effect‚ of penalization (hyperopic overcorrection) on eye growth and refractogenesis Elena P. Tarutta, Laboratory of Myopic Studies, Helmholtz Research Institute of Eye Diseases, Moscow, Russia. Purpose: to study the effect of permanent lasting overcorrection of hyperopia on eye growth and refraction in children. Material and Methods: 18 children (36 eyes) with microesotropia and amblyopia averagely aged 5.8 years with the mean R=+2.77 D on the better eye, +3.2 D on the worse, BCVA 0.82 and 0.4, axial length (AL) 21.1 mm and 20.9 mm, respectively, were followed up. The correction lens power of the better seeing eye exceeded the refraction by 1.5-2.5 D in order to reduce VA down to 0.2-0.3, whilst for the worse eye it was equal to refraction. The control group was composed of 15 children of a similar age with the mean R=+3.14D and the mean AL 21.2 mm, who wore regular correction lenses. Results. 3 months after start of wearing glasses, a 1.25-2.0 D increase of hyperopia degree as measured with autorefractometer was marked in 14 cases on the “penalized” eye, which drew the eye’s refraction closer to the power of the penalizing lens, brought about an increase in VA and made the eye predominant. Obviously, the adaptive effect was achieved due to the change of the habitual accommodation tonus and to manifestation of residual hyperopia. After a respective increase of the positive lens power, the effect was not repeated. By the end of the 5-year follow-up period (average age 10.8) the refraction and AL parameters showed no noticeable change: respectively, 2.73 D and 21.5 mm on the better eye and 3.34 D and 21.3 mm on the worse eye. In the control group, the mean refraction was 1.91 D at the end of the follow-up period and the mean AL was 22.7 mm. Conclusion. Full correction and overcorrection of hyperopia delayed age-related refraction increase and AL growth in children who wore penalizing spectacles on a permanent basis.

The x-ray density of sclera and shape of the eyes with myopic refraction Narine V. Khodzhabekyan1, Elena P. Tarutta1, Vladimir V. Valsky2 1 Laboratory of Myopic Studies, Moscow Helmholtz Research Institute of Eye Diseases, Moscow, Russia. 2 Ophthalmic Oncology Dept., Helmholtz Institute of Eye Diseases, Moscow, Russia. Purpose: To study the X-ray density of sclera and shape of the eyes with myopic refraction in children and teenagers. Materials and methods: The study was carried out by computed tomography (CT) of the orbits (Siretom-2000, Siemens, Germany). X-ray density of sclera was measured in Hounsfield units (HU) in three sites: in a posterior pole and in external and internal parts of equatorial zone. Measurement of the ocular dimensions along the two cardinal axes: anterior-posterior (A-P) and horizontal-transversal (H-T) was done also. The study was conducted on 150 eyes of 80 patients 7-15 years old with myopia from 0.5D to 12.0D. The control group included 25 eyes with em-metropia and low hyperopia. Results and conclusions: A derangement of scleral biophysical properties was revealed in eyes with myopia. A significant decrease of scleral density in myopic eyes was revealed as compared to the control group. The increase of myopic refraction was accompanied by authentic reduction of scleral density. The congenital myopia revealed the lowest parameters of density that will be coordinated with eye fundus state of the patients. The density of sclera in eyes with complicated (PVCRD) myopia was lower than in eyes of non-complicated. The parameters of scleral density in progressive myopia were lower than in non-progressive. Prognostical criteria for myopia pro-gression were worked out. The spheric shape of eye (A-P/H-T=1.0) occurred most frequently in all three degrees of myopia. The compressed ellipsoid (A-P/H-T<1.0) was the second frequent while the number of eyes in the shape of the elongated ellipsoid (A-P/H-T>1.0) increases with the progression of myopia.

28


The muscular balance of eyes and AC/A ratio in patients with myopic anisometropia Narine V. Khodzhabekyan, Laboratory of Myopic Studies, Moscow Helmholtz Research Institute of Eye Diseases, Moscow, Russia. Purpose: To study the phoria state and AC/A (accommodative convergence/accommodation) ratio in patients with myopic anisometropia. Materials and methods: 32 patients (23 female, 9 male): aged from 9 to 32 years (the mean age 17.7) with myopic anisometropia were examined. The mean refraction of the more myopic eye was -6.39D (-1.75D to -14.5D). The mean refraction of the less myopic eye was -3.5D (-0.5D to -12.0D). The mean refraction difference between two eyes was 3.28D. All the patients showed binocular vision in best-corrected spectacles and contact lenses. Heterophorias were determined using prism-compensator and Maddox-rod. The AC/A ratio were measured by the gradient method. Results and conclusions: The phoria state for distance in best-corrected spectacles: orthophoria was revealed in 38% of cases, exophoria and esophoria equally in 31% of cases. The dominant types of muscular balance in contact lenses for distance were determined to be orthophoria (17%) and esophoria (83%). The phoria state for near: 1. without correction - orthophoria occurred in 18% of cases, exophoria in 75% and esophoria in 7% of cases; 2. in best corrected spectacles - orthophoria (44%), exophoria (44%) and esophoria (12%). 3. The dominant type of muscular balance in contact lenses for near was determined to be esophoria. The average value of AC/A ratio was 1.94 prism.dptr./dptr. The mean value of AC/A ratio in control group was 3.12 prism.dptr./dptr. We suppose that low values of AC/A ratio are peculiar for the myopic anisometropia.

Functional state of the retina in children with congenital myopia Gayane A. Markossian, Inna V. Zolnikova, Elena P. Tarutta, Laboratory of Myopic Studies, Helmholtz Research Institute of Eye Diseases, Moscow, Russia. Purpose: To study bioelectrical activity of the retina in children with congenital myopia. Material and Methods. 15 patients (30 eyes) with congenital myopia aged 10-15 were examined. The degree of myopia, which was first diagnosed at the age of 1-2 years, varied from -6.0 to -20.0 D in spherical equivalent (mean =-12.5 D), and the maximum correction visual acuity was 0.2-0.8 (mean=0,5). Maximum, macular and multifocal electroretinography (mfERG) was registered with a Roland Consult electroretinograph (Germany) equipped with Retiscan software. Results. Of 15 patients, 3 had congenital myopia combined with congenital stationary night blindness, which was confirmed by a minus negative macular, maximum and multifocal electroretinography. 6 patients showed normal bioelectrical activity of the central and the peripheral parts of the retina, 7 patients revealed a decrease in the bioelectrical activity of the retina, 1 patient had a reduced amplitude of the macular ERG, and the amplitude of the P1 component of mfERG was reduced in the central 10°. In 6 patients a reduction of the macular and maximum ERG amplitude was noted together with a reduction of the mfERG amplitude in the central and the peripheral segments, which evidences pathology of the rod/cone system of the retina. Conclusions. ERG data show that congenital myopia is a heterogenic group. Some patients reveal congenital stationary night blindness and other functional disorders of outer layers of the retina. In a substantial part of subjects with congenital myopia, reduced visual acuity is not accompanied by a violation of bioelectric activity and is most probably related to refractive amblyopia.

29


Linkage analysis for some myopia loci in Russian families with autosomal dominant complicated high myopia Gayane A. Markossian1, Natalia Vasserman2, Svetlana Tverskaya2, Alexander Polyakov2, Evgeny Ginter2, Elena P. Tarutta1, Olga A. Panteleeva1, Martin Hergersberg3, 1

Laboratory of Myopic Studies, Moscow Helmholtz Research Institute of Eye Diseases, Moscow, Russia. Research Centre for Medical Genetics, Moscow , Russia. 3 Zentrum für Labormedizin, Kantonsspital Aarau, CH-5001 Aarau, Switzerland. 2

High myopia is a refractive error greater than or equal to 6 diopters. Although there is evidence for a strong genetic contribution to the pathogenesis of high myopia, no susceptibility genes are known and it is possible that there are some genetic forms of this disease. Several loci for high myopia have been mapped: MYP1 on Xq28, MYP2 on chromosome 18p, MYP3 on chromosome 12q, MYP4 on chromosome 7q, and MYP5 on chromosome 17q but no genes except X-linked myopia are known. Purpose: to investigate Russian families in which some of the members belonging to two or more generations are affected with autosomal dominant complicated myopia (PVCRD, CCRD). No families were large enough for a whole genome screening to be reasonable, but linkage analysis for the known loci could be done. Probands and methods: DNA samples were extracted from peripheral blood leukocytes from 23 affected and unaffected siblings from four Russian families. Polymorphous markers close to MYP2 and MYP3 were analyzed using amplification fragments length polymorphism method. Results: In all families but one, we have excluded the MYP3 locus as a possible disease locus. In three families the MYP2 locus was not excluded as a possible disease locus. TGF-beta-induced factor gene is localized at this locus and considered as a candidate gene for high myopia. Conclusions: We propose to investigate all autosomal myopia loci for linkage analysis and study possible gene candidates to establish gene factor predisposition for high myopia in Russian families.

Design of a prospective clinical trial of the use of bifocal soft contact lenses to control myopia progression (CONTROL) Thomas A. Aller, Private Practice, San Bruno, California, USA. Introduction. CONTROL (Control Of Nearsightedness Trial Of Lenses) is a one-year, controlled, prospective, double-masked clinical trial comparing the myopia progression in children with near point eso fixation disparity while wearing single vision or simultaneous vision bifocal two-week disposable soft contact lenses. While there have been many clinical trials of the use of bifocal and progressive spectacles in the control of myopia progression (1-5), CONTROL will be the first prospective clinical trial of bifocal contacts used in this regard. It will also be the first truly double-masked bifocal lens study. Previous research by the author (6-8) has suggested that bifocal soft contact lenses may be unusually effective in myopia control. Method. Approximately 100 children aged 8 to 18 will be recruited. Subjects are to be matched for age, sex, ethnicity, and refractive error and will be randomly assigned to either the bifocal or the single vision contact lens group. The contact lenses in each group are identical in material (58% water), modality, color, size, and lens markings and have obscured labels. After determining eligibility through a vision screening, subjects return for a comprehensive evaluation with dry and cycloplegic automated (Marco) and subjective refractions, binocular assessment (phoria and fixation disparity) auto and manual keratometry, topography, pachymetry, pupillometry, axial lengths and AC depth (Zeiss IOL Master). Subjects return for a diagnostic lens evaluation with both single vision and bifocal contact lenses. The bifocal prescription is selected to maximally reduce the eso fixation disparity at near, while maintaining adequate distance visual acuity. Both prescriptions are then sent to the research assistant, who then makes the lens assignments. Subjects return for dispensing, training and a lens evaluation, and are scheduled back at two weeks, six months and one year. The two groups will be evaluated and compared for changes in refractive error and ocular measures. References: Gwiazda, J et al.(2003). IOVS, 44, 1492-1500. Parssinen O, Hemminki E, and Klemetti A.(1989) British J Ophthal, 73, 547-51. Goss DA, Grosvenor T.(1990) Optom Vis Sci, 67, 637-40. Fulk GW, Cyert LA, Parker DE.(2000) Optom Vis Sci, 77, 395-401. Fulk GW, Cyert LA, Parker DE.(2002) J Am Optom Assoc, 73, 470-476. Aller TA, Grisham JD.(2000) Optom Vis Sci, 77(12s), 187. Aller TA. (2002) Optom Vis Sci, 79(12s), 179. Aller, TA (2003) Optom Vis Sci, 80(12s),

30


Acquired progressive eso- and hypotropia in high myopia Yury Z. Rosenblum1, Svetlana G. Chernysheva1, Tamara P. Kashchenko2 1 Optometry and Ophthalmoergonomics Laboratory, Moscow Helmholtz Research Institute of Eye Diseases, Moscow, Russia. 2 Strabismus Dept., Helmholtz Institute of Eye Diseases, Moscow, Russia. Purpose: To conduct clinical, physiological and histopathological examinations and optimize surgical treatment of squint in high myopia. Methods: Six patients with eso- and hypotropia in high myopia were examined using imaging techniques: computer tomography (CT), echography, histology. These patients developed progressive binocular myopia of 20 D and higher, axial length averaged to 30 mm, and transversal axis to 26 mm. Results: The major CT findings included a medial shift of superior rectus and a downward shift of externus rectus, an increase in medialis rectus diameter, shortening of externus rectus diameter, arcuate curvature of inner walls of the orbit due to the pressure of enlarged eyeballs, and a sharp curvature of optic nerves. All changes were more expressed in nonfixing eyes. All patients were surgically treated for squint (first esotropia, then hypotropia.) Plastic surgeries were not performed because of vertical rectus insufficiency. Histological examination of the muscles showed dystrophy, with interlayers of fatty and fibrous tissues. After surgery, we observed improvements in the angle of squint; curvature of the optic nerves, motility of eyes and visual acuity. Discussion: In our opinion, in progressive myopia the eyeballs may behave in either of the two ways: (1) the eyeball protrudes out (the axial axis is elongated), or (2) the eyeball is “driven” into the orbit (the transversal axis is elongated). In our cases, the latter takes place. We believe that the term heavy eye syndrome common in literature is incorrect and should be replaced by another term, driven-in eye syndrome, because the clinical picture is determined by a deep position of the eyeball in the orbit rather than by a downward shift of the eye. Conclusions: The findings suggest that the disease can be diagnosed and treated at an early stage before it comes to severe atrophies and contractures of extraocular muscles.

Prevalence of refractive errors in university students Rafaela Garrido1, V. Domínguez1, R. Gómez de Liaño2, D. Martínez1, 1

Departamento de Medicina Preventiva, Universidad Complutense, Madrid, Spain. Departamento de Oftalmología, Facultad de Medicina. Universidad Complutense, Madrid, Spain.

2

Purpose: To evaluate the prevalence of refractive errors in a population of university students in Spain and to compare the prevalence between first year students (18 years old) and final year students (22-24 years old). We have also described the refractive errors distribution curve of the population. Methods: A cross-sectional study of 270 university students of three different areas of academic study was conducted,130 first year students and 140 final year students. The refractive error was determined under cycloplegic (1% cyclopentolate) autorrefraction after given inform consent. Myopia was defined as a spherical equivalent ≤ -0.50D and hyperopia as a spherical equivalent ≥+0.75D. Data from the right eye of each student was analysed with SPSS. Results: The prevalence of refractive errors conditions in the group of first year students was found to be: 31.3% myopes, 29% hyperopes and 32.1% emmetropes. The prevalence in the group of final year students was found to be: 49% myopes, 20.3% hyperopes and 25.9% emmetropes. The mean refractive error was – 0.20 D in first grade students and – 0.98 D in final year students. Difference between both groups was statistically significant (p<0.001 Mann Witnney test). Conclusions: There is a significant difference in refractive errors among first and final year students, with higher prevalence of myopia in final year students and smaller prevalence of hyperopia. This indicates a high prevalence rate of adult-onset myopia and postulates the influence of intensive near work in the development of myopia. References: 1- Adams DW, McBrien NA.(1992) Optom Vis Sci.69,467-473. 2- Bimbiene R, Bluziene A et al. (2000). 8th International Conference on Myopia. 76-79. 3- Iribarren R, Iribarren G et al, (2002). Curr Eye Res. 25(5), 309-15. 4- Kinge B, Midelfart A. (1998). Acta Opthalmol (Copenh) 76, 692-695. 5- Luke L-K L, YungFeng S et al.(1996) Optom Vis Sci. 73, 495-8. 6- Luke L-K L, Chien-Jen C, et al. (1988). Acta Opthalmol Suppl 185, 29-33. 7- McBrien NA, Adams DW. (1997). Investig Opthalmol & Visual Science. 38:,321-333. 8Midelfart A, Aamo B, et al (1992). Acta-Ophthalmol-Copenh. 70(3), 317-22. 9- Rose K, Smith W, et al, (2003). Clin Exp Ophthalmol. 29, 116-120. 10- Saw S-M, Katz J, et al (1996) Epidemiolo-Rev.18(2), 17587. 11- Saw S-M, Hong R-Z, et al. (2001) J. Pediatr Ophthalmol Strabismus.38, 149-155. 12- Sharma V, Chaudhary KP. (2000) 8th International Conference on Myopia., 15-20 13- Wojciechowski R, Congdon N, et al, (2003). Ophthalmology.110 (2), 365-75. 14- Zylbermann R, Landon D, Berson D.(1993). J. Pediatr Ophthalmol Strabismus. 30, 319-322.

31


The influence of lighting on accommodation responses in emmetropes and myopes Edward Mallen, Charlotte Hazel, Priti Kashyap, Department of Optometry, University of Bradford, Bradford, West Yorkshire, UK. Purpose: To investigate the effect of natural and artificial light sources on the accuracy of the accommodative stimulus/response function in myopic and emmetropic subjects. Examine the variability of the static accommodation response under different lighting conditions in emmetropes and myopes. Methods: Static accommodation responses (0 to 4 D) to a high contrast letter target presented within a Badal system were measured with a Shin-Nippon SRW-5000 infra-red autorefractor. Accommodation measurements were carried out under 5 target illumination conditions (natural daylight, tungsten, tungsten halogen, low pressure mercury fluorescent and compact fluorescent) in 10 emmetropes and 10 myopes. Results: Accommodative Error Indices (AEI) were calculated from the response error and correlation coefficient of the accommodative response between 1D and 4D for each subject under all lighting conditions. Repeated measures ANOVA revealed that the AEI was not significantly different (P>0.05) between refractive error groups. Myopes showed greater variability in AEI under all artificial lighting conditions compared to emmetropes. Conclusions: Type of light source for near tasks does not have a significant effect on the accuracy of static accommodation responses in emmetropes or myopes. Myopic subjects show greater variations in accommodative stimulus/response function under all lighting conditions. The greater variability of AEI in myopes may be explained by active progression of refractive error in this group. Further work is suggested to evaluate the effect of artificial light sources on dynamic accommodation responses, with particular attention being paid to potential differential effects between stable and progressing myopes.

Target vergence related increases in accommodation microfluctuations in myopia and emmetropia Mhairi Day1, Niall C. Strang1, Dirk Seidel1, Lyle S. Gray1, Edward Mallen2 1 Department of Vision Sciences, Glasgow Caledonian UniversityGlasgow Caledonian University, Glasgow, Scotland, UK. 2 Department of Optometry, University of Bradford, Bradford, UK. Aim: Models of the accommodation system suggest that inaccurate responses to both near and distance targets play a role in the development of myopia. Accommodation microfluctuations provide a sensitive measure of the accuracy of sustained accommodation responses. Microfluctuations have been found to increase with target vergence across the accommodation range. In this study we investigate accommodation microfluctuations in myopic and emmetropic subjects for a range of accommodative stimulus levels. Methods: 20 (10 myopic and 10 emmetropic) healthy young adult volunteers with less than 0.50D of astigmatism participated with informed consent in the study. The subjects viewed a high contrast Maltese cross target through a +5D Badal lens in photopic conditions. Accommodation stimulus levels ranging from 0-4D in 1D steps were presented randomly. Accommodation was measured continuously over a period of two minutes using a Shin-Nippon SRW-5000 infrared autorefractor at a sampling rate of 52Hz. Myopic subjects were fully corrected using daily disposable soft contact lenses. Results: Significant (p<0.05) increases in the magnitude of accommodation microfluctuations were found with increasing target vergence in both the myopic and emmetropic groups. Power spectrum analysis revealed that these increases could predominantly be attributed to an increase on the power of the low frequency components (<=0.5Hz). No significant differences in rms value were found between the refractive groups. Conclusions: The increase in rms value with increasing target vergence appears to be similar in both refractive groups and is modulated by the low frequency components of the fluctuations.

32


Voluntary Accommodation Responses in Emmetropia and Myopia Dirk Seidel, Mary Ann Craig, Lynsay Dunlop, Lyle S. Gray, Niall C. Strang Department of Vision Sciences, Glasgow Caledonian University, Glasgow, Scotland, UK. Purpose : It has been demonstrated previously that under blur-only viewing conditions steady-state accommodation responses are reduced in myopic individuals (MYO) compared to emmetropes (EMM). In natural viewing, where a full set of cues is available to the accommodation controller no differences between MYOs and control groups have been found. This suggests that reflex accommodation errors in myopic eyes are compensated by other accommodation cues during real life viewing. In this experiment we investigate whether one of the other cues, voluntary accommodation, is modified in myopes to compensate for the reduced reflex accommodation. Methods : 20 (10 MYO and 10 EMM) healthy young adult volunteers (mean age 21±2.2 years) with normal vision participated in the study. The subjects viewed high contrast Snellen letters randomly at 5 distances ranging from 0.25 to 5 m and steady state accommodation responses were recorded using a Canon R1 optometer. Measurements were repeated in total darkness with the subjects imagining that they were looking at the targets shown earlier. The accommodation response elicited by voluntary accommodation in the dark was then compared to the steady state response. Results: Both refractive groups exhibited reduced steady state accommodation responses at near (i.e lag) but no differences in accommodative accuracy were found between the two refractive groups (p>0.1). Both EMMS and MYOs showed reduced accommodation responses in the voluntary condition (p<0.0001) with no apparent variation between the refractive groups (p>0.1). Voluntary responses showed considerable inter-subject variability with some individuals exhibiting accurate responses and others showing almost no voluntary response to near targets. Voluntary input appeared to be unrelated to the size of the reflex accommodation error. Conclusions: The results suggest that myopic subjects may not use voluntary input to compensate for the reduced blur sensitivity of their accommodation controller.

A Unique Case of Self-induced Myopia and Monocular Diplopia Richard McCollim, Scripps Clinic, La Jolla, California, USA. Purpose: To test the hypothesis that the action of the extraocular muscles, particularly the superior obliques, can elongate the globe. Method: A viewing device was constructed consisting of two identical photographic transparencies depicting a visually rich pattern. When the subject looked through the device, each eye viewed one of the transparencies. The transparencies were then incyclorotated, i.e. as seen by the subject, the right-side image was rotated counterclockwise and the left-side image clockwise. To maintain fusion of the two images, each eye must then rotate in the same direction as the image it is viewing, i.e. the upper end of the vertical meridian of each eye leans nasalwards. The movement of incyclorotation is opposed by the check ligaments and other fascial structures of the orbit. If an effort is made to maintain fusion, traction of the superior obliques, which wrap part way around the globe, exert pressure in the general area of the equatorial meridian and, presumably, elongate the globe. Results: The existing myopia increased by some 5 D. An unexpected result was that the uncorrected acuity became nearly emmetropic (20/25). The subjective vision consisted of a nearly sharp image superimposed on a highly blurred image. This dual mode of vision could be interpreted as a combination of high myopia and near emmetropia in each eye. Conclusion: A possible cause was pressure from the superior obliques transmitted through the sclera to the vitreous, forcing it against the posterior surface of the lens and flattening its peripheral area. This may have been an extreme case of the normal spherical aberration that occurs when the eye accommodates. Dual vision persisted for several years, which suggests that a highly deformed lens is extremely slow to revert to its original state.

33


A cross-sectional study of anisometropia Jeremy A. Guggenheim1, Xuejiao Qin2, 1 School of Optometry & Vision Sciences, Cardiff University, Wales, UK. 2 Department of Ophthalmology, Qilu Hospital of Shandong University, Shandong, China. Purpose: To explore associations of anisometropia with age, sex, and refractive error, in a cohort of 90,884 subjects attending UK optometry practices. Method: Subjects were classified into 10-year interval age groups. Anisometropia was defined as a >= 1.00 D difference in spherical power between eyes, and further classified as: “Mild” >=1.00 D & <2.00 D, “Moderate” >=2.00 D & <3.00 D, or “Severe” >=3.00 D. All analyses were repeated for anisometropia defined on the basis of mean spherical equivalent (MSE) power. Results: There was an increase in both the median level and the prevalence of anisometropia with age (p<0.001). The median level and the prevalence of anisometropia also increased with the degree of spherical refractive error in the less ametropic eye (p<0.001, for myopes and hyperopes). In general, there were slightly more myopic anisometropes than hypermetropic anisometropes (mostly those in the mild severity class). In view of the sample size, the effect of sex on anisometropia level and prevalence was not considered significant (p>0.001). The frequency distribution of refractive error differed significantly between the right eyes of non-anisometropes and the less ametropic eyes of anisometropes. The frequency distribution of power in the less ametropic eyes of anisometropes also differed with anisometropia severity level. However, whilst statistically significant, these latter effects were surprisingly subtle. The results of all analyses were similar irrespective of whether anisometropia was defined on the basis of spherical or MSE power. Conclusions: As noted in previous studies, the prevalence and magnitude of anisometropia was found to increase with age and with the degree of refractive error. Anisometropia did not vary significantly between males and females. The frequency distribution of refractive error in the less ametropic eyes of anisometropes is leptokurtotic and centred close to zero. However, the frequency distribution does vary with age and with anisometropia severity.

34


Changes in main anatomical and optical characteristics of the eye during overnight orthokeratology lens wear. Tatiana Y. Verzhanskaya1, Elena P. Tarutta1, D. G. Uzunyan2, D. S. Mirsayafov3 1 Laboratory of Myopic Studies, Moscow Helmholtz Research Institute of Eye Diseases, Moscow, Russia. 2 IRTC Eye Microsurgery, Moscow, Russia. 3 Doctor Lens Clinic, Moscow, Russia. Purpose: To assess refractive and biometric changes in subjects undergoing overnight orthokeratology. Methods: Six young adult subjects with low and middle myopia (mean = - 3,88 D) were fitted with reversegeometry lenses ®, Contex, Inc., which were worn in both eyes for 3 months on an overnight basis. Refractive error and corneal refractive powers were measured with autorefractometry and autokeratometry. Lens thickness and axial length were recorded with ultrasound A-scan; anterior chamber depth (measured from endothelium), corneal epithelium thickness and anterior chamber angle (using method, suggested by Pavlin et al.) with ultrasound biomicroscopy. According to this data, the vitreous depth and the position of iris-lens diaphragm were calculated. All parameters were statistically analyzed by t-tests and compared with that of pre-treatment. Results: Significant central corneal flattening (3.02 +/- 0.75 D; p < 0.01) were found after 3-month period of lens wear. Changes in corneal epithelium thickness were also statistically significant. In the center epithelial thinning reached 20 +\- 10 micron (p<0,001) and was accompanied by thickening of epithelial layer in midperipheral zone (2,5 mm from the corneal center) by 30 +\- 10 micron (p<0,001). Significant enlargement of anterior chamber angle, measured both in degrees (3,45 +/- 4,05; P<0,01) and in micron (56 +/- 0,05; P<0,01 when measured at 250 micron from scleral spur and 50 +/- 0,01 at 500 micron) was registered. There was a trend towards increase of anterior chamber depth, and decrease of vitreous depth, but these changes were statistically insignificant. Iris-lens diaphragm also showed a trend to move backwards. Conclusions: Orthokeratology causes central corneal epithelial thinning and midperipheral thickening due to its molding and redistribution in response to the tear film forces generated behind reverse-geometry lenses. The effect of anterior chamber angle enlargement is an evidence of possible biomechanical changes during orthokeratology procedure.

Facility of accommodation in children with and without Myopia. Ashok Pandian,1 Les Donovan,1 Padmaja R.Sankaridurg,1 Thomas John,1Paul Mitchell,1,2 Kathyrn Rose,1,2 Daniel O’Leary,1,3 Deborah F.Sweeney1 1 Vision Co-operative Research Centre, Sydney, Australia 2 Centre for Vision Research, Westmead Millenium Institute, University of Sydney, Australia 3 Anglia Polytechnic Institute, Cambridge, United Kingdom Purpose: To investigate the characteristics of facility of accommodation of children attending primary school and to determine differences if any in the characteristics between children with and without myopia. Methods: The speed of the positive and negative accommodative responses at distance and near were measured as the number of cycles cleared over a 1 min period using –2.0D/ plano semi-automated flipper for distance and +/-2.0 D semi-automated flipper for near. Also, the amount of time taken to identify the target at both distances with both positive and negative accommodative stimuli was measured as the response time in milliseconds. Data for 654 primary school aged children participating in the Sydney Myopia study is presented. Results: The mean age of the population was 7.0 ± 0.6 yrs (5 to 8 yrs). Of the 654 children, 11 were myopic (1.7%), 164 were hyperopic (21.7%) and 474 were emmetropic (73%). Mean distance facility was significantly lower in the myopic group (5.3cycles/min) in comparison to the hyperopic (7.0cycles/min) and emmetropic group (6.9cycles/min). Also, the response times for positive accommodative response and negative accommodative response was greater in the myopic group in comparison to hyperopic and emmetropic groups (p=0.024 and 0.006 for distance positive and negative accommodative response, ANOVA). No such differences were seen for the near accommodative facilities between the groups. Conclusions: Our data suggests that the accommodative facility at distance is abnormal in myopes and confirms the findings reported by O’Leary and Allen, 2001 where an abnormal accommodative response to blur at distance was observed in adult myopes. Reference: O’LearyDJ, Allen PM (2001). Ophthal Physiol Opt, 21(5), 352-355.

35


Differential protein expressions in the emmetropisation of chick eyes Thomas C. Lam1, Samuel C.L. Lo2, Chi-Ho To1 1 Centre for Myopia Research, Department of Optometry and Radiography, The Hong Kong Polytechnic University, Hong Kong. 2 Proteomic Task Force, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hong Kong. Purpose: To investigate the differential retinal protein expressions in the lens-induced myopic chick eyes by a proteomic approach. Methods: The samples were recovered by using a sequential extraction approach based upon the differential solubility (by Tris buffer and Urea & CHAPS containing buffer) of the retinal proteins. Proteins were separated on IPG strips with different pH ranges by two dimensional gel electrophoresis (2DE). The protein profiles were visualized by Mass Spectrometry (MS) compatible silver stain. The 2DE retinal protein maps were compared and analysed using Melanie4 gel matching software. Retinal protein spots were excised and in-gel trypsin digested. Mass spectra were acquired from a Bruker Autoflex MALDI-TOF MS in reflectron mode and the resulting peptide maps were searched against the NCBInr and MSDB databases via the Mascot search engine for protein identification. Results: the majority of detectable retinal proteins (> 85%) could be separated on narrower pH5-8 IPG range. Melanie4 analysis showed a strong similarity in the protein profiles between proteins solubilised in the two extraction buffers while a number of proteins could only be detected in more aggressive buffer. Between the defocus and control groups, one protein spot which had been identified by MALDI-TOF peptide mass fingerprinting was found consistently differentially expressed between the two groups. Presence of the specific protein in the Tris buffer indicates the cytosolic nature of the protein. The specific protein was also found to be related to the growth phase. Conclusion: In the present study, we have shown the differential protein profiles of the chick retinae in the buffers of different solubilisation power. One candidate protein which may involve in the emmetropisation of the chick eyes was identified for the first time using a proteomic approach.

Longitudinal study of myopia progression of Hong Kong Chinese microscopists Patrick WK Ting,1,2 Carly CS Lam,1 Marion E. Edwards,1* Katrina L Schmid2 1. Centre for Myopia Research, Department of Optometry and Radiography, The Hong Kong Polytechnic University. Hong Kong. 2. School of Optometry, Queensland University of Technology, Brisbane, Australia. * Retired Purpose: This study sought to determine the progression rate of myopia in Hong Kong Chinese microscopists and whether progression was related to the microscopy task. Method: Thirty-six microscopists (age=31.7±3.8 yr, SER=–4.75±3.5 D) and 12 non-microscopists (age=32.5±5.3 yr, SER=–3.81±2.58 D) were followed for a two-year-period. Refractive error (both cycloplegic and noncycloplegic), ocular dimensions and binocular vision (distance and near phoria and fusional reserves) were monitored at six months intervals. Microscopists were also questioned as to the amount of microscopy they performed. Results: The two yearly change in refractive error for microscopists and non-microscopists were –0.11±0.31 D (paired t-test, t=2.220, p=0.033) and −0.40±0.43 D (t=3.180, p=0.0088) respectively. The axial length of microscopists increased by 0.16±0.21 mm (t=4.728, p<0.0001) and non-microscopists by 0.23±0.27 mm (t=2.924, p=0.0138). There was a significant difference in the magnitude of the refractive error change of microscopists and non-microscopists (unpaired t-test, t=2.157, p=0.0476). There was no significant change in the binocular vision measures of either group. There was no relationship between the magnitude of microscopist’s myopic shifts and the daily amount of microscopy they performed (r=−0.233, p=0.171). Conclusion: The refractive error and axial lengths changes in this group of Hong Kong Chinese microscopists was not clinically significant and was much less than that reported for United Kingdom microscopists (even though the ages of the groups were similar, UK age = 29.7 yr, range 21 to 63 yr). We propose that this difference may be due to different subject characteristics, for example differences in the temporal pattern of environmental myopia development. It does not seem that microscopy is a high-risk myopogenic task in this ethnic group. Acknowledgement: The work described in this paper was supported by the Research Grants (Project No. A352) of the Area of Strategic Development Fund, The Hong Kong Polytechnic University and QUT International Doctoral Scholarship.

36


Remote results of local antioxidant treatment of progressive myopia Elena N. Iomdina1, Alexandra V. Lazuk1, Natalia V. Khvatova2, Natalia N.Slyshalova2 1 Laboratory of Myopic Studies, Moscow Helmholtz Research Institute of Eye Diseases, Moscow, Russia. 2 Ophthalmological Dept., Ivanovo Children's Hospital, Ivanovo, Russia. In progressive myopia, processes of peroxide oxidation of lipids are intensified, while the system of antioxidant protection is weakened. This may cause myopia progression and peripheral vitreochorioretinal dystrophies (PVCRD) development [1]. Purpose: to evaluate clinical effectiveness of a noninvasive locally applicable antioxidant medication, ophthalmic medicinal films (OMF), for prevention of myopia progression and complications. Methods. OMFs, containing an immobilized compound of emoxypine and its structural analogue, pyridoxine hydrochloride, deposited in biosoluble polymer, were administered daily during 15 days twice a year (2-4 cycles in all) to 50 eyes of 25 patients (8 male, 17 female) aged 11-17 (mean age 13.6) with progressive myopia of low (14 eyes), moderate (19 eyes) and high (17 eyes) degree (mean R= -4.8±0.3 D) and mean axial length (AL) = 25.1 ±0.15 mm. 13 eyes had various PVCRDs. The untreated control group included 50 eyes of 25 patients (9 male, 16 female) aged 10-17 (mean age 13.4) with progressive myopia of low (20 eyes), moderate (25 eyes) and high (5 eyes) degree (mean R= -4.1±0.4D), and AL=24.4 ±0.2 mm. 4 eyes had PVCRDs. The patients of both groups were examined thoroughly every 6 months for 5 years. Results. By the end of the follow-up period 1) the treated group showed a 0.8 D increase in the mean R= -5.6±0.3 D, a mean yearly progression gradient 0.26 D, a 0.4 mm mean increase in AL=25.5±0.17 mm, new PVCRD developed in 7 eyes (14%); 2) the control group showed a 1.4 D increase of the mean R=-5.5±0.4 D, a mean yearly progression gradient 0.54 D (twice as high as the treated group); a 0.7 mm mean increase in AL=25.1±0.17 mm, new PVCRD developed in 22 eyes (44%, 3 times as often as in the treated group). Conclusion. Local antioxidant therapy slows down myopia progression and effectively prevents its complications. References: 1. Iomdina E.N., Kushnarevich N.Yu., Vinetskaya M.I., Tarutta E.P., Lazuk A. V. (1998). Antioxidant therapy of progressive and complicated myopia in children. Proc. of VII Intern. Conference on Myopia. Taipei, Taiwan, 171172.

A cross sectional study of the effect of age on myopia AA Yekta, MH Bahreinitoosi, M Tavakoli, Department of Optometry, Mashhad University of Medical Sciences, Parastar Avenue, Ahmadabad Street, Mashhad, Iran. Purpose: The aim of this investigation was to evaluate the effect of age on prevalence and amount of myopia by cross sectional study. Methods: Patients visiting the optometry department, Mashhad University of Medical Science were refracted by using standard objective and subjective refraction methods. A clinical sample of 2410 patients (1205 man and 1205 woman) was preformed ranging from 1 to 97 years of age in steps of 5 years. Spherical equivalents were computed and analyzed by using SPSS software. Results: The results of this investigation showed that prevalence and amount of myopia increase with increasing of age until 20 years in men and woman. These changes are not significant until 40 years of age and then by beginning of presbyopia, the prevalence and amount of myopia decrease. Conclusions: The results of this study demonstrate a statistically significant increase in the prevalence and the amount of myopia during the school and the early adult years and decrease during the presbyopic years.

37


Keynote Address: Clinical trials of lens treatments for myopia control Jane Gwiazda The New England College of Optometry, Boston, MA USA The purpose of this presentation is to review recent clinical trials of spectacle lens treatments for slowing the progression of myopia in children. Well-designed studies of bifocals or progressive addition lenses (PALs), compared to the conventional spectacle treatment for myopia of single vision lenses (SVLs), show treatment effects ranging from 0.14 to 0.57 D at the end of 2 to 3 years. In many of the trials, the treatment effect was observed at the end of the first year and was sustained at the same level for the duration of the study. While most of these results are statistically significant, they do not warrant a change in clinical practice. Additional analyses of data from the Correction of Myopia Evaluation Trial (COMET), a multi-center, randomized clinical trial of PALs vs SVLs in the United States, showed that statistically significant 3-year treatment effects were found for children with poor accommodation in combination with near esophoria (0.64D), lower amounts of myopia (0.48D), shorter reading distances (0.44D), or more hours of weekly near work (0.42D). These treatment effects were significant at one year and became larger between 1 and 3 years. The results suggest a role for retinal defocus in myopia progression. In clinical practice in the United States children with poor accommodation and near esophoria often are prescribed PALs or bifocals to improve visual performance. Results of this study suggest that such children, if myopic, may have an additional benefit of slowed progression of myopia. The results also suggest that lens treatments are likely to be effective in subsets of myopic children with specific risk profiles.

38


The prevalence and progression of myopia in Chinese-Canadian children attending an optometric practice Desmond Cheng1, Katrina L. Schmid1, George C. Woo2 1 School of Optometry, Queensland University of Technology, Brisbane, Australia. 2 Department of Optometry and Radiography, The Hong Kong Polytechnic University, Hong Kong, China. Purpose: Chinese children living in Hong Kong and Taiwan are known to have an extremely high risk of developing myopia. By the time children are 12 years old 50-60% are myopic and the average amount of myopia is -1.00D1,2. Between 7 and 12 years the average annual progression rate is 0.32D1. We sought to determine whether the prevalence of myopia and its progression in Chinese children living elsewhere was also high. Methods: The refraction data of 1468 (40% of the group in Mississauga) 6 to 12 years old, Chinese children living in Mississauga, Ontario, Canada were collated from optometric records (Dr. Desmond Cheng & Associates, 1997 to 2003). Data was grouped into 6 age bands: 6 to 7, 7 to 8, 8 to 9, 9 to 10, 10 to 11 and 11 to 12 years. Refractive error distributions, the prevalence of myopia, the magnitude of refractive error shifts and the incidence were determined. Myopia was defined as a spherical equivalent refraction (SER) ≤ -0.50D based on a non-cycloplegic subjective refraction. Results: At each age band the refractive error distribution was significantly different from a normal distribution. The leptokurtosis was greatest at age 6 (83.1% of children’s refractions were between -0.75D and +0.75D) and decreased at older ages (27.7% at age 12). The prevalence of myopia increased from 24.9% at age 6 (-0.02±1.02 D) to 71.2% at age 12 (-1.97±2.04D). The annual progression of myopia was -0.39D, -0.53D, -0.47D, -0.58, -0.59, and -0.52 respectively. Conclusions: Chinese children living in Canada are just as susceptible to myopia development as those living in Asian countries; migration to Canada does not lower their risk. Perhaps these children experience the same academic pressures as those children living in Asia. Treatments that prevent or slow myopia progression would also be beneficial to these children. References: 1.Edwards, M.H. (1999). Ophthal. Physiol. Opt. 19, 286-294. 2.Yap, M., Wu, M., et al (1994). Clin. Exp. Optom. 77, 8-14.

Spectacle lens defocus alters myopia progression rate in schoolchildren John R. Phillips, Department of Optometry and Vision Science, The University of Auckland, Auckland, New Zealand. Purpose: To investigate a monovision spectacle correction as an alternative to bifocals for reducing accommodation in childhood myopia. Methods: Eighteen 11 year-old children (initial refractions: -1.00 D to -3.00 D mean sphere) were fitted with a monovision spectacle correction. The dominant eye was corrected for distance, the other eye was uncorrected or, if the refractive imbalance exceeded 2.00 D, corrected to give an effective add of 2.00 D. Cycloplegic autorefraction and ocular biometry (A-scan) measures were made approximately every 8 months for up to 30 months. Dynamic retinoscopy was used to assess accommodative status while reading with the monovision prescription. Results: Children accommodated to bring reading material into focus in the distance-corrected (dominant) eye rather than using the near-corrected eye to read. Thus, assuming consensual accommodation (Koh & Charman, 1998), the near-corrected eye suffered relative myopic defocus at all levels of accommodation. Linear, mixed effects modelling of the inter-eye differences in refraction and axial eye dimensions showed that axial myopia progression in the near-corrected eyes was significantly slower than in the distance-corrected eyes. The mean difference in myopia progression rate equalled 0.37 D/yr (95% CI = 0.57 to 0.18 D/yr, P = 0.0005); the mean difference in vitreous chamber elongation rate equalled 0.13 mm/yr (95% CI = 0.19 to 0.08 mm/yr, P = 0.0001). No significant inter-eye differences developed for lens thickness (P = 0.383) or anterior chamber depth (P = 0.513). Data are for 13 children as 5 were lost to follow-up. Conclusions: This study shows that retinal image defocus influences eye growth and refractive development in schoolchildren in a manner consistent with the effects of optical defocus in animal eyes (Hung, Crawford, & Smith, 1995; Zhu, Winawer, & Wallman, 2003). It supports the idea that childhood myopia progression could in principle be controlled by optical means (Wildsoet, 1997). References: Hung, L. F., Crawford, M. L., & Smith, E. L. (1995). Nature Medicine, 1(8), 761-765. Koh, L. H., & Charman, W. N. (1998). Ophthalmic & Physiological Optics, 18(3), 254-262. Wildsoet, C. F. (1997). Ophthalmic & Physiological Optics, 17(4), 279-290. Zhu, X., Winawer, J. A., & Wallman, J. (2003). Investigative Ophthalmology & Visual Science, 44(7), 2818-2827

39


Prediction of myopia beyond the influences of refractive error Karla Zadnik, Lisa A. Jones, G. Lynn Mitchell, John R. Hayes, Donald O. Mutti, College of Optometry, The Ohio State University, Columbus, Ohio, USA. Purpose. The Orinda Longitudinal Study of Myopia (OLSM) collected data on children from 1989 to 2001 beginning in grade one through grade eight to determine factors associated with the development of myopia. In previous work we have used receiver operator characteristic (ROC) curves to determine the area under the curve of predictive models for the optimum way of identifying potential myopes. These models are driven by refractive error of children at grade three, leaving little explanatory power for the other potential predictors. This analysis evaluates other potential predictors, such as nearwork and parental myopia for their predictive power without baseline refractive error. Methods: Subjects seen in third grade who were free from myopia were eligible to be included in this analysis. A myope was defined as having a refractive error at least -0.75 D in both meridians. Model building used a stepwise proportional hazard analysis using SAS statistical software. A variable was added to the model when it had the maximum -2 log number likelihood score until no further reduction in the -2 log likelihood was seen. An index number was derived from the final model to generate a ROC with its area under this analysis. Results: One hundred ten children became myopes between the third grade and their last visit. The model obtained included the following variables: reading hours, number of myopic parents and number of hours playing sports. The area under the curve for this model was 0.69, which was significantly different from chance. The model including child’s refractive error at third grade yields an area under the curve of 0.90. Conclusions: While the model using a child’s refractive error has a higher predictive ability, a model with reading hours, number of myopic parents, hours playing sports also had significant predictive ability.

40


Keynote Address: Myopia and environment Ernst Goldschmidt, Danish Institute for Myopia Research, Hilleroed, Denmark. In many parts of the world changes in prevalence of myopia have been observed from one generation to the next. Both increases and decreases have been reported. It is unlikely that the changes have a genetic origin so the purpose of the present study is to search for environmental factors influencing myopia development and progression . Methods Based on literature and own investigations, the following associations and correlations have been studied: • Myopia and occupation (textile workers and compositors) • Myopia and school curricula (academic activities) • Myopia and sport • Myopia, general disease and diet Results In textile workers controlling weaving texture myopia development has been reported with intervals since 1906. Head and eye movements may play an important role, as may the constantly changing retinal images. From some places in central Europe and Scandinavia a decrease in myopia prevalence has been reported to happen when school-hygienic measures like better lighting, more physical training and abolishment of gothic print in schoolbooks were implemented. In school children and young adults physical activities may in themselves reduce myopia progression but also the induced pauses in academic activities may be beneficial. Publications on a possible correlation between diabetes and myopia appeared twenty years ago. Chronic hyperinsulinaemia may play a key role in the pathogenesis of juvenile-onset myopia because of its interaction with hormonal regulation of vitreal growth. Some of the observed changes in myopia prevalence from one generation to the next could be due to changes in diet. Conclusion There is strong evidence that myopia development and progression can be influenced by environment. Recent data indicate that less demanding academic programs during early schooling may reduce the amount of myopia. Similarly more physical activities and reduced carbohydrate intake may benefit the vision of schoolchildren. References: Goldschmidt, E. (2003)The mystery of myopia. Acta Ophthalmol.Scand. 81: 431-36. Simensen, B. and L. O. Thorud. (1994)Adult-onset myopia and occupation. Acta Ophthalmol (Copenh) 72: 469-71.

41


The long-term effect of macular translocation surgery with 360-degree retinotomy for myopic choroidal neovascularization Takashi Fujikado1, Yasuo Tano2, Masahito Ohji2, Yasushi Ikuno2 1 Department of Visual Science and Ophthalmology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan. 2 Department of Ophthalmology, Osaka University, Suita, Osaka, Japan. Purposes: Although several treatments, such as photodynamic therapy, are now available for myopic choroidal neovascularization (CNV), most of the treatments are aimed to stabilize the visual degradation. By a macular translocation surgery, the fovea is shifted from the CNV to the healthy pigment epithelium and the vision is able to be recovered. However, the enlargement of chorio-retinal atrophy and/or recurrence of CNV occur occasionally after the surgery. In this study, we investigated the long-term visual outcome of this surgery. Method: Twenty seven eyes of 27 consecutive patients with myopic choroidal neovascularization who underwent macular translocation surgery with 360-degree retinotomy and were followed up more than 2 years were examined. The average follow-up period was 42.2 ± 10.8 months. Strabismus surgery was executed in all eyes to align the horizontal axis. Pre- and postoperative best-corrected visual acuity (BCVA) was examined. Results: The average BCVA (Log MAR) was 0.76 ± 0.34 preoperatively and 0.53 Â± 0.46 at the postoperative final visit. The final BCVA improved more than 0.2 log MAR unit in 16 eyes, unchanged in 6 eyes, worsened more than 0.2 log MAR unit in 5 eye. The final visual acuity was better than 20/50(reading acuity) in 13 eyes and was batter than 20/30 (driving acuity) in 7 eyes. Retinal detachment occurred in 7 eyes after surgery, which was successfully reattached in the second surgery. The recurrence of extrafoveal CNV occurred in two eyes. Conclusion: Although care should be taken for the possibility of retinal detachment after surgery, macular translocation with 360-degree retinotomy is generally effective to improve the visual acuity in eyes with myopic CNV even in the long-term follow-up. References: Fujikado, T., Ohji, M., et al. (2001): Am. J. Ophthalmol. 131(1):101-110 Tano, Y. (2002): Am. J. Ophthalmol., 134(5):645-660 Soubrane G (2004): VIP study group. Five-year results of verteporphin photodynamic therapy in pathologic myopia. ARVO abstract

Degenerative myopia, the risk of visual disability and the identification of criteria for therapeutic intervention. Brian Ward1, Elena P. Tarutta2, 1 Ophthalmology, Stanford University Medical Center, Retinal Diagnostic Center, Campbell & Stanford University Medical Center, Stanford, California, USA. 2 Laboratory of Myopic Studies, Helmholtz Research Institute of Eye Diseases, Moscow, Russia. Purpose: Degenerative Myopia is a major cause of visual disability, worldwide. This study examines the risk of vision loss in the various ages of life, provides a clinical threshold for therapeutic intervention and evaluates axial length measurement as a practical tool for the study of such cases. Method: A total of 463 eyes with high axial myopia were evaluated. A prospectively designed set of examinations and clinical tests was used. Those collecting the data had no knowledge of the purposes in which it might be used. Information on patient age, refractive error and axial length measurements were of particular relevance to this study. Results: Ametropia was compared to axial length. The degree of visual disability was determined for each age group. Early onset high myopia was associated with increased childhood vision loss. Age and axial length correlated positively with the risk of adult vision loss. Adult eyes with significant myopia macular degeneration had axial lengths in excess of 26 mm. In the over 60 year age group, visual acuities ranged from 20/20 to finger counting. The average 28 mm eye had a visual acuity of 20/40 and the average 30 mm eye an acuity of 20/60. Conclusions: * Axial length is a useful tool for the evaluation of degenerative myopia. * Early onset of axial myopia increases vision loss in childhood. * Age and axial length correlate positively with the risk of vision loss in adults. * The data indicates that to prevent late-adult vision loss therapies should be designed to limit axial extension to no more than 26 mm. * Effective genetic, medical or surgical interventions which limit scleral growth or stretching could reduce later vision loss even when the threshold axial length had already been exceeded. * Axial length stability is relevant to all forms of optical ocular correction, including the rapidly developing field of refractive surgery.

42


Progressive myopia in children: To cure or not to cure? Elena P. Tarutta, Laboratory of Myopic Studies, Helmholtz Research Institute of Eye Diseases, Moscow, Russia. Purpose: to estimate the effectiveness of laser and surgical methods of treating progressive myopia in children. Methods. Children with rapidly progressing myopia were divided into two groups. The test group (240 patients, 480 eyes, average age at start 9.1 years, myopia degree 5.5+-1.1 D, progression rate 1.2 D/year) received surgical treatment that included repeated sclera reinforcement interventions: low-invasive (SSI) at the age of 8-9 and scleroplastic operations at the age of 10-12. Additionally, transscleral low-power laser stimulation of the ciliary muscle was given 2 times a year using an infrared laser MACDEL-09 to increase blood supply and metabolic processes in eye tissues. The control group (106 patients, 212 eyes, average age at start 9.0 years, myopia degree 5.3+-1.3 D, progression rate 0.98 D/year) did not receive such treatment. There were no changes in the eye fundus in either of the two groups at the start. Patients were examined every 6 months for 10 years with a thorough checkup of the periphery of the eye fundus and given argon laser photocoagulation (LC) of the retina if indicated. Results. The average progression rate during the 10-year period was 0.38 D/year in the test group and 0.8 D/year in the control group; final degree of myopia was 9.3D and 13.3D, respectively. The occurrence of PVCRD was 33.7% and 56.1%, respectively, in particular, lattice dystrophy and breaks 10% and 20.8%, breaks with subclinical retinal detachment 0.8% and 2.4%. The need for LC was marked in 4.6% of eyes (6.7% of patients) in the main group and 13.2% in the control. Conclusion. The elaborated system of repeated sclera reinforcement interventions and low-power laser treatment combined with preventive peripheral LC results in a reduced progression rate and lessens the risk of PVCRD development and retinal detachment in children and adolescents with progressive myopia.

Is IQ associated with myopia in children? Seang-Mei Saw1, 2, Lin Yu, Say-Beng Tan3, Daniel Fung4, Kee-Seng Chia5, Donald T. H. Tan1, Richard A. Stone6, 1 National University of Singapore, Singapore; 2 Singapore Eye Research Institute, Singapore. 3 Division of Clinical Trials and Epidemiologic Sciences, National Cancer Centre, Singapore, Singapore. 4 Department of Child and Adolescent Psychiatry, Institute of Mental Health, Singapore, 5 Department of Community, Occupational and Family Medicine, National University of Singapore, Singapore, 6 Department of Ophthalmology, University of Pennsylvania School of Medicine, Philadelphia, USA. Purpose: To evaluate the association between intelligence and myopia in children. Methods: Cycloplegic refraction and ocular biometry parameter measures, including axial length, vitreous chamber depth, lens thickness, anterior chamber depth and corneal curvature were obtained in 1,204 Chinese school children aged 10 to 12 years from 3 schools who were participants in the Singapore Cohort study Of the Risk factors for Myopia (SCORM). Intelligence quotient (IQ) was assessed using the non-verbal Raven Standard Progressive Matrix test. Results: After controlling for age, gender, school, parental myopia, father's education and reading, the odds ratio of myopia [spherical equivalent (SE) at least -0.5 Diopter (D)] for children with IQ in the fourth quartile compared with children in the first quartile was 2.4 [95% confidence interval 1.7, 3.4]. Controlling for the same factors, children with higher IQ scores had significantly more myopic refractions (-1.86D for children with IQ in the fourth quartile compared with -1.24D for children with IQ in the first quartile; p=0.002) and longer axial lengths. Conclusion: IQ may be an independent risk factor of myopia and this relationship may not merely be explained by increased reading among myopes. The complexity of the relationships between IQ, reading and myopia warrant additional studies to clarify any cause-effect relationship. References: 1. Rosner, M., Belkin, M. (1987). Arch Ophthalmol.1987,105,1508-1511. 2. Hirsch, M.J. (1959) Am J Optom Arch Am Acad Optom. 1959,36,12-21. 3. Grosvenor, T. (1970)..Am J Optom Arch Am Acad Optom. 1970,47,355-361. 4. Mutti, D.O., Mitchell, G.L. et al (2002). Invest Ophthalmol Vis Sci. 43,3633-3640. 5. Saw, S.M., Hong, C.Y., Chia, K.S., Stone, R.A., Tan, D. (2001) Nearwork Lancet 357,390. 6. Saw, S.M., Chua, W.H. et al (2002). Invest Ophthalmol Vis Sci. 43,332-339. 7. Teasdale, T.W., Fuchs, J., Goldschmidt, E (1988). Lancet 2,1351-1354.

43


Keynote address: Molecular Genetics of High Myopia". Dr. Terri Young Children’s Hospital of Philadelphia, Philadelphia, PA, USA High myopia is a common complex trait eye disorder, with implications for blindness due to increased risk of retinal detachment, chorioretinal degeneration, premature cataracts, and glaucoma. Mapping studies have identified at least 4 loci for non-syndromic autosomal dominant high myopia at chromosomes 18p11.31, 12q22-q23, 17q21, and 7q36, and one Xlinked locus at Xq28. This presentation will discuss the progress in determining implicated genes for high myopia.

44


Testing for association between MYOC and myopia susceptibility in Hong Kong Chinese population WC Tang,1 SP Yip, 2 MKH Yap,1 KK Lo,1 PW Ng,1 PS Choi,1 SY Lee2 1 Department of Optometry and Radiography and 2Biomedical Science Section, School of Nursing, The Hong Kong Polytechnic University, Hong Kong SAR, China. Purpose: Myopia is a risk factor for glaucoma (Grodum et al., 2001). Mutations in the myocilin (MYOC) gene were responsible for some cases of primary open-angle glaucoma. Association between an MYOC polymorphism and myopia has been reported in the Singapore Chinese population (Wu et al., 1999), but could not be replicated in the Hong Kong Chinese population (Leung et al., 2000). Both studies used case-control approach. Our objective was to test the possible association between MYOC and myopia susceptibility in Hong Kong Chinese with a family-based association test. The family-based approach is robust to population stratification, which can produce false positive association in case-control studies. Methods: Chinese nuclear families (n=157) were recruited, each comprising two parents and at least one myopic offspring (≤ –5.0DS for both eyes). Ocular examination and venous blood collection were performed for all family members. DNA was extracted from blood samples for genotyping the microsatellites (GT repeats) located at the 5’ promoter region and 3’ untranslated region (UTR) of MYOC. Transmission/disequilibrium test (TDT) was performed with the software FBAT to test for association between these polymorphisms and myopia. Results: Three alleles were found for the promoter microsatellite. The results revealed increased transmission of the short allele (13 repeats; Z = 2.613, P = 0.00900 for additive model; Z=2.297, P = 0.02164 for dominant model), but decreased transmission of the long allele (15 repeats; Z = -3.922, P = 0.00009 for additive model; Z = -4.535; P = 0.00001 for dominant model) to myopic offspring. Five alleles were found for the 3’UTR microsatellite, but did not show association with myopia. Conclusion: Association was demonstrated between the MYOC promoter micosatellite and myopia with familybased association study. Our results supported the positive finding in Singapore. The negative finding in another study might be due to small sample size. References. Grodum K, Heijl A and Bengtsson B. (2001). Acta Ophthalmol Scand, 79: 560-6. Leung Y F, Tam P O, et al (2000). Hum Mutat, 16: 533. Wu H, Yu XH, Yap EP (1999). Invest Ophthalmol Vis Sci, 40:S600. Abstract 3148.

Methodology of the genes in myopia (GEM) study P.N. Baird1,2, T. Couper 1,3, H.R. Taylor1,2, P. Garoufalis 1,2 Centre for Eye Research Australia, University of Melbourne, Australia. 2 Vision CRC, Sydney, NSW 2052 3 Melbourne Excimer Laser Group.

1

Purpose: Myopia is the most common human eye disorder affecting approximately 1 in 5 Australians.1 It is a complex disease involving both genetic and environmental factors. No genes have so far been identified for myopia but several loci have been reported2,3. Previous studies have concentrated on high myopia and no study has so far been conducted on an Australian population. Methods: The Genes in Myopia (GEM) Study was established to identify the gene/s involved in the development of myopia through family linkage studies. Individuals with moderate to severe myopia (at least - 3 dioptres in the least myopic eye) and a family history of the disease are invited to participate. Index cases have been recruited through the surgeons of the Melbourne Excimer Laser Group (MELG). Available patients consist of approximately 2,000 myopic individuals who have undergone refractive surgery at MELG, and match our inclusion criteria. Each participant undergoes an ophthalmic assessment that includes a measure of best-corrected visual acuity, objective and subjective refraction, corneal topography, axial length and slit lamp exam. A questionnaire is administered to all participants, and a blood sample taken for DNA analysis. Results: The present participation rate is approximately 25%. 786 individuals from the MELG database have so far been invited to participate with 105 families already recruited. The degree of myopia in the index cases ranged from -3 to -15 dioptres. In the families a total of 119 females and 72 males between the ages of 13 - 85 years, (mean of 47 years), have been examined. The majority of these participants were born in Australia (70%), followed by Central Europe (15%), Western Europe (10%) and Asia (5%). Conclusion: The GEM study provides an opportunity to identify genes involved in the development of myopia. References: 1. Wensor, M., McCarty, C. A., & Taylor, H. R. (1999). Archivies of Ophthalmology, 117, 658-663. 2. Young, T. L., Ronan, S. M. et al.(1998). American Journal of Human Genetics, 63, 1419-1424. 3. Young, T. L., Ronan, S. M. et al (1998). American Journal of Human Genetics, 63, 1419-1424.

45


A systematic unifying approach to identifying myopia susceptibility genes SP Yip,1 WC Tang,2 KK Lo,2 PW Ng,2 PS Choi,2 MKH Yap2 1 Biomedical Science Section, School of Nursing, and 2Department of Optometry and Radiography, The Hong Kong Polytechnic University, Hong Kong SAR, China. Purpose: Common myopia is a complex trait with both environmental and genetic risk factors contributing to its genesis. This study aims to identify myopia susceptibility genes that are likely to have small to moderate effects individually. Methods: Two complementary approaches were adopted. One approach was based on affected sib-pair (ASP) method. An efficient 2-stage study was designed on the basis of sample splitting and grid tightening. A second approach was based on genetic association studies using a candidate gene strategy. Both family-based and population-based association studies were used while the candidate genes were selected for testing on the basis of myopia biology. Results: Chinese nuclear families (n=200) with two parents and at least two severely myopic (at least -5.0 D) siblings were recruited. These family samples were used for both the first stage of the ASP approach, and the family-based association studies. A separate exercise was carried out to recruit 300 unrelated high myopes (at least -8.0 D) and 300 unrelated emmetropes (at most ±0.5D) for the population-based association study approach. Ocular measurement and venipuncture were performed for each recruited subject. DNA was extracted from blood for genotyping of genetic markers. Microsatellite markers are the genetic markers of choice for ASP analysis using a genome scan approach while single nucleotide polymorphisms are ideal markers for genetic association studies. Conclusions: We have adopted a very systematic global approach to mapping myopia susceptibility genes. ASP analysis will give a coarse candidate chromosomal region for further testing in the second stage of ASP, and for follow-up for candidate gene selection and testing in association studies. Family samples can be shared between some strategies. Family-based association studies are performed to avoid the confounding due to population stratification and to replicate population-based association studies.

How genetic is school myopia? Ian Morgan1, Kathy Rose2, 1 Visual Science Group, Research School of Biological Sciences, Australian National University, Canberra, Australia. 2 School of Applied Vision Sciences, University of Sydney, Sydney, NSW, Australia. Purpose: To review the evidence for genetic and environmental determination of myopia. Methods: PubMed searches were carried out using combinations of the terms family, gene or genetic, parental, heritability, environment, prevalence and myopia. Other references were obtained from reference lists in the papers. Results: The evidence for genetic determination of school myopia comes primarily from family correlations, including the greater correlation observed in monozygotic as compared to dizygotic twins. However these measures potentially confound shared genes with shared environments. Calculated heritability values are high in twin studies, but rest on contestable assumptions, under conditions of restricted environmental variation. Three lines of evidence suggest that these high heritabilites substantially over-estimate the role of genetic variation: 1)non-twin sibling and parent-offspring correlations are significantly lower than for dizygotic twins, 2)correlations decline with greater age gap and under conditions were there is marked environmental change between generations, 3) particularly in East Asia, the prevalence of myopia has changed rapidly. It has been suggested that East Asians may be more susceptible to environmental risk factors. However, populations of East Asian origin show wide variations in the prevalence of myopia, from very low in rural areas, to exceptionally high as in major cities. In contrast, Singaporean Indians (of Caucasian origin), exposed to the “myopigenic” environment of Singapore show a much higher prevalence of myopia than is seen in India - close to that seen in Singaporean Chinese. Many different racial/ethnic groups show evidence of environmental impacts on the prevalence of myopia. Conclusions: While the high heritabilities for myopia obtained in twin studies may indicate some genetic contribution to myopia, most of the evidence suggests that powerful environmental effects are responsible for the rapid changes in prevalence that have been seen recently, as well as for the marked differences in prevalence in different parts of the world.

46


A genome-wide linkage analysis suggests PAX6 is linked to myopia in a sample of dizygotic twins C.J. Hammond, T. Andrew, Y-T Mak, T.D. Spector Twin Research and Genetic Epidemiology Unit, St Thomas’ Hospital, London, UK Purpose: We have previously reported a strong genetic influence on refractive error (heritability 85%) in an unselected sample of 506 volunteer twin pairs. We demonstrated significant linkage at four loci in a genome-wide screen of 221 dizygotic sib-pairs, with the maximum linkage peak (LOD 6.1) at chromosome 11p13. The PAX6 gene is fundamental to eye development, and has been the sole gene implicated in aniridia; mutations cause this congenital abnormality, which may show progressive changes in life. The location of PAX6 at 11p13 suggested this as a candidate gene responsible for the myopia linkage signal in this area. Methods: A search of available public databases of single nucleotide polymorphisms (SNPs) in and around the PAX6 gene identified 29 possible SNPs. Of these, 5 could not be set up, and the resulting 24 SNPs were examined in a subsample of 20 twins. 7 SNPs showed no polymorphisms, resulting in 17 SNPs (on average 1 per 2kB) examined. Haplotype Linkage Disequilibrium tagging was used to examine blocks of SNPs making up the same haplotype. These SNPs were then genotyped in 190 dizygotic twin pairs to test for linkage and association. Results: Haplotype tagging identified 5 SNPs (tSNPs), which explained 0.999 of the haplotype diversity arising from 17 common allele frequency SNPs. Analysis of the tSNP genotypes and haplotypes using QTDT showed strong evidence of linkage for all markers (minimum of chi-sq = 7.5. p=0.006). No evidence of population stratification was observed. In tests of total phenotypic association to the markers, there was no significant association. Conclusions: The quantitative trait of spherical equivalent shows strong evidence of linkage to PAX6 but no association, suggesting that genetic variant(s) are located in the vicinity of the gene, probably within regulatory or promoter regions of PAX6.

The gene encoding fibulin-1 (FBLN1): A candidate gene for early-onset high myopia with recessive inheritance Martin Hergersberg1, L. Bernasconi1, C. Ruegg1, K. K. Seitkamalovna2, Evgeny Ginter3, Svetlana Tverskaya3, Alexander Polyakov3, Elena P. Tarutta4, Gayane A. Markossian4, Olga A. Panteleeva4, Brian Ward5, G. M. Sarra6, Svyatova G7, A. Huber1 1 Zentrum für Labormedizin, Kantonsspital Aarau, CH-5001 Aarau, Switzerland 2 Department of Pediatric Ophthalmology, Almaty, Kazakstan. 3 Research Centre for Medical Genetics, Moscow, Russia. 4 Laboratory of Myopic Studies, Helmholtz Research Institute of Eye Diseases, Moscow, Russia. 5 Ophthalmology, Stanford University Medical Center, Retinal Diagnostic Center, Campbell & Stanford University Medical Center, Stanford, California, USA. 6 University Eye Clinic, Inselspital, Berne, Switzerland 7 Laboratory of Medical Genetics, Almaty, Kazakstan Background: There is evidence for a strong inherited contribution to the pathogenesis of high myopia, but no susceptibility genes are known. Recently, a chromosomal region containing a candidate gene encoding fibulin-1 (FBLN1) has been localized in a family with four (of eight) children with early-onset high myopia developing into a vitreoretinal dystrophy later in life. Fibulin-1 is a component of the extracellular matrix, it is expressed in many tissues including the sclera, and it is an interesting candidate gene for high myopia susceptibility. Probands and methods: The FBLN1 gene was analyzed by denaturing HPLC and by sequence analysis in the DNA of affected and unaffected members of the family, and in the DNA from 21 probands with high myopia from Kazaksthan. A real-time RT-PCR assay verifies the presence of FBLN1 transcripts in the RNA of peripheral lymphocytes and will be applied for quantitation of FBLN1 transcripts in patients with high myopia. Results: A 10 centiMorgan region on chromosome 22 was homozygous for the microsatellite alleles in the four affected siblings. Molecular analysis of FBLN1 did not identify a mutation in this family. Mutation and expression analysis of FBLN1 in the DNA of high myopia probands is in progress. Conclusions: Gene polymorphisms contributing to myopia susceptibility are difficult to identify. A combination of mutation and expression analysis is a reasonable strategy to test the hypothesis that changes in FBLN1 gene activity have a role in the pathogenesis of high myopia.

47


Keynote Address:

Ocular aberration and myopia

W.N.Charman Optometry and Neuroscience, UMIST, PO Box 88, Manchester M60 1QD, UK A number of authors have suggested that myopes may have higher levels of monochromatic aberration than emmetropes and that ocular aberration may, in some way, be involved in the development at least some cases of myopia. The effects of aberration on through-focus modulation transfer and ocular depth-offocus are outlined, together with possible mechanisms whereby aberration could interact with accommodation to contribute to myopia development. Available experimental measurements of aberrations of different refractive groups are discussed. Taking into account the likely pupil diameters in photopic vision, it is concluded that it is unlikely that higher-order monochromatic aberrations can play a causative role in myopia development.

48


A Longitudinal Study of Monochromatic Aberrations Change in Children with Increasing Myopia Kwan WCK1, Yip SP1,2, Yap MKH1 1 Centre for Myopia Research, Dept of Optometry & Radiography, 2 Biomedical Science Section, School of Nursing, The Hong Kong Polytechnic University, Hong Kong. Purpose: To investigate the change of monochromatic aberrations in children with increasing myopia. Methods: This study investigated refractive error and monochromatic aberration changes in a group of 200 Hong Kong school children from age 6 to 11 years over a 2-year period. Monochromatic aberrations were measured in a dark room with the cycloplegic pupils larger than 5mm using the Complete Ophthalmic Analysis System (COAS) Wavefront Analyzer. The subjects were refracted by cycloplegic auto-refraction using the Shin-Nippon SRW5000 autorefractor. Results: Of the 200 subjects, about half of them finished the first year investigation until now. Monochromatic aberrations of the twelve subjects (7 boys and 5 girls) with increasing myopia more than one diopter in the first year were analyzed. Of the 12 Zernike terms displayed (second to fourth order), root mean square (RMS) of Z(2,0), Z(2,2) and Z(4,0) were significantly different between the first visit and the 1-year visit (paired t-test: t=10.956, p<0.0001; t=2.786, p<0.05; t=3.301, p<0.01, respectively). The RMS’s of Z(2,0) and Z(2,2) increased with increasing myopia while the RMS of Z(4,0) decreased with increasing myopia. The RMS of fourth-order aberrations significantly decreased with increasing myopia (paired t-test; t=3.593, p<0.005). No significant difference was found in coma, third-order aberrations and total higher order aberrations (third to fourth) between the first visit and the 1-year visit. Conclusions: Of the higher order aberrations (third to fourth), spherical aberrations and fourth-order aberrations were found to be significantly decreased with increasing myopia. This may have implications for refractive development. This relationship can be further studied when this 2-year period ended.

The noble art of measuring axial eye length: A mini-survey, to include also the utility of the IOLMaster Hans C. Fledelius, University Eye Dept E 2061, Copenhagen University Hospital, Rigshospitalet, 2100 Copenhagen, Denmark. Purpose: Survey ultrasonic axial eye measuring methods and compare recent results with partial coherence interferometry (PCI; equipment IOL-Master) in selected morphologically difficult eyes of patients. Methods: 35 years’ personal experience in ultrasonic axial length measurement is briefly reviewed. There are time sequence vs. frozen methods, immersion vs. contact techniques, and manual vs. automated acceptance. Recently we challenged our longitudinal oculometry results in the Danish high myopia project (Goldschmidt & Fledelius) comparing with IOL-Master readings, and we further compared the two technical principles in a series of 38 young Marfan patients. Results and conclusions: Technically all eyes could be measured by ultrasound, while a 5-7% rejection rate (ERROR) applied to the PCI method. Individual differences between methods ranged -0.4 to 0.7mm, but groupwise the difference averaged less than 0.1 mm. The advantages of the PCI method for clinical studies are non-contact / a very high reproducibility / optical axis safeguarded (in eyes with centric fixation). To our knowledge, coherence interferometry based methods have not yet been developed for experimental animal research purposes.

49


The relation between growth of axial length and higher order aberrations in school children Yoshinori Nakai Baptist Eye Clinic, Kyoto Prefectural Universityof Medicine, Kyoto, Japan Purpose: Growth of axial length causes progress of myopia. And blurred vision on retina induces axial elongation. The purpose of the present study was to examine the relationship between higher order aberrations and axial length, to clarify the development of myopia. Methods: We measured the axial length with IOL-Master (Carl Zeiss), and measured the higher order aberrations with Wavefront analyzer (TOPCON) of 195 children’s left eyes (96 eyes of 9 years old and 99 eyes of 11years old). We examined the relations of axial length, corneal higher order aberrations and ocular higher order aberrations. Results: The axial length was correlated with coefficient of ocular spherical aberration and RMS error of ocular higher order aberrations (p<0.01). The axial length of 11 years old (23.0±1.15 mm) were greater than that of 9 years old (23.5±0.81 mm), and the corneal spherical aberrations of 11years old were greater than that of 9 years old. Conclusion: This suggests there is a relationship between progression of myopia and higher order aberrations. Growth of axial length may link corneal shape and reduction of ocular spherical aberration

Retinal steepness vs. myopic shift in children Gregor Schmid, Pennsylvania College of Optometry, Elkins Park, USA and Vision Co-operative Research Centre, University of New South Wales, Sydney, Australia. . Purpose: Retinal steepness (RS; posterior pole eye shape) and relative peripheral defocus (RPD; peripheral minus central defocus) were shown to correlate. It was proposed that RS influences myopic shift (decrease in hyperopic or increase in myopic central refraction) in children, presumably by peripheral defocus inducing compensatory eye growth. The purpose of this study was to determine the correlation between RS and myopic shift in children. Methods: RS and RDP were determined with Optical Low Coherence Reflectometry and autorefractometry, respectively, by measuring eye length (EL) and Spherical Equivalent Refraction (SER) axially and at 15Âº temporally, inferiorly and superiorly at baseline and 1 year in right eyes of 63 children (7-15 yrs) during cycloplegia. 17 were myopic (>-0.50D), 23 emmetropic (+/-0.50D), and 23 hyperopic (>+0.50D). The correlation between baseline RS and myopic shift, and differences between refractive groups in RS, axial EL, axial SER, and changes over 1 year were analyzed. Results: In myopic eyes only, baseline RS was associated with myopic shift. RS was significantly different between refractive groups (one-factor ANOVA), myopic eyes having the steepest and relatively most hyperopic shapes. RS did not change in all refractive groups, and no child changed refractive group. Axial EL and SER differed significantly between refractive groups (one-factor ANOVA). Myopic and emmetropic eyes elongated significantly (paired t-test), but only emmetropic eyes exhibited significant myopic shift. Eye elongation and myopic shift were approximately the same in the refractive groups. Conclusions: Baseline RS predicts myopic shift in myopic eyes only. This suggests that in initially non-myopic eyes, factors other than peripheral defocus are involved in myopia onset and that visually-driven growth control mechanism(s) differ from those in myopic eyes. The observation that no child developed myopia, and eye shapes did not change significantly may be due to the relatively short measurement period of one year.

50


Should axial length measured with the IOL-Master become the primary outcome measure in clinical trials of myopia progression? Mark A. Bullimore, Kathleen S. Reuter, G. Lynn Mitchell, Lisa A. Jones, College of Optometry, The Ohio State University, Columbus, Ohio, USA. Purpose: The IOLMaster uses partial coherence interferometry to measure axial length. We have previously shown the superior repeatability of the IOLMaster over ultrasound (Sheng et al., 2004). The 95% limits of agreement (LoA) for the IOLMaster (-0.06 to +0.05 mm) correspond to less than ±0.25 D (assuming that 1 mm = 2.50 D). Here we report longitudinal axial length data from a cohort study of adult myopes. Methods: The Study of Progression of Adult Nearsightedness (SPAN) is a five-year cohort study to determine the risk factors associated with adult myopia progression. Annual testing includes axial length measurement with the IOLMaster (mean of three readings) and cycloplegic auto-refraction. We compared axial length measurements from the first annual follow-up visit with baseline measurements in 275 subjects. Results: At the first annual follow-up visit, axial length was within 0.15 mm of baseline in 96.4% of subjects. Eight subjects showed axial elongation between 0.17 and 0.31 mm and five of these showed corresponding refractive error changes (-0.40 to -1.85 D). Two subjects showed modest reductions in axial length (-0.23 and -0.24 mm). Conclusions: In the vast majority of subjects, axial length measurements are consistent across study visits. In a small proportion of subjects, significant axial elongation occurs, and is confirmed by autorefraction in most patients. We propose that the IOLMaster should be the primary outcome measure in clinical trials of myopia progression for three reasons: First, in dioptric terms, its repeatability exceeds that of auto-refraction (Sheng et al., 2004). Second, it is relatively unaffected by accommodation making cycloplegia an optional part of the protocol (Drexler et al., 1998). Finally, in clinical trials involving contact lenses it will be relative unaffected by corneal changes thus avoiding the need for a wash-out period to assess refractive error changes (Walline et al., 2001). References: Sheng H, Bottjer CA, Bullimore MA.. Optom Vis Sci 2004;81:27-34 Drexler W, Findl O, et al. Invest Ophthalmol Vis Sci 1998;39:2140-7. Walline JJ, Mutti DO et al. Optom Vis Sci 2001;78:223-33.

Myopia is axial until otherwise proven: A discussion of clinical entities apparently at variance Hans C. Fledelius, University Eye Dept E 2061, Copenhagen University Hospital, Rigshospitalet, 2100 Copenhagen Ø, Denmark. Background: With the advent of ultrasonic measurements it was established, that myopia is usually axial, and index myopia mainly anecdotal. Purpose: to present and discuss previously investigated myopic patient series with significant index components as a general feature of their entities. Material and Methods: Axial ultrasonic measurements were carried out in a) surviving children of pre-term delivery, with emphasis on myopia of prematurity, b) so-called diabetic myopia in adults, and c) a recent series of young Marfan patients (n=38). Results: In addition to the probably curtailed axial growth in myopia of prematurity, a peaked cornea, a flatter anterior chamber, and a thicker lens all contribute to the myopia on the index side. In adults with diabetic myopia lenses thicker-than-for-age may be held responsible. Marfan patients generally had flat corneas and axial lengths close to normal, and their myopia is probably explained by high lens powers. Conclusions: Environmental factors have been at least partly operational in the first two entities of myopia, whereas the morphometric features of Marfan eyes are probably purely genetic.

51


Spherical aberration and refractive error measurement Daniel J. O’Leary, Hema Radhakrishnan, Baskar Theagarayan Department of Optometry and Ophthalmic Dispensing, APU, Cambridge UK Vision CRC, UNSW, Sydney Australia. Purpose: To examine how spherical aberration affects the measurement of refractive error in humans. Materials and methods: Best subjective refractive error (maximum plus for maximum acuity) was obtained in a group of young subjects, and the optimum refraction was determined for a range of spatial frequencies by determining contrast thresholds and defocus. In a second group, spherical aberration (SA) was varied by applying aspheric soft contact lenses with known amounts of SA; COAS refraction was measured, as well as subjective refraction and autorefraction (PowerRefractor and Nidek AR600). Results. Subjects with SA showed a myopic shift in optimum focus (proportional to the amount of SA) for medium and low spatial frequencies in comparison with their subjective refraction, however the optimum focus for high spatial frequencies corresponded to the optimum subjective refraction. When SA was varied using contact lenses, the COAS value for the refraction was always close to the subjective refraction, however both the Nidek and PowerRefractor reading changed considerably. Conclusion: The optimum subjective refraction for Snellen Letters corresponds closely to the axial refraction (as measured by the COAS aberrometer) and is not influenced greatly by SA. The high-frequency optimum focus is the preferred focus. Objective refraction by the PowerRefractor is affected by SA, probably because it takes into account the data from the whole pupil.

52

10th International myopia conference 2004 Index to Authors Allen Aller Amedo Andrew Bahreinitoosi Baird Bantseev Benavente Perez Bernasconi Bhana Bradley Brinkworth Bullimore Charman Cheng Chernysheva Cheung Chia Cho Choi Chui Collins Couper Craig Davies, Day Dayton Domínguez Donovan Dunlop Edwards Fernandes Fledelius Fritsch Fujikado Fung Garoufalis Garrido Giblin Gilmartin Ginter Goldschmidt Gómez de Liaño Gray Guggenheim Gwiazda Hammond Harb, Hayes Hazel Hergersberg Hirohara

PM TA AO T MH PN V A L P DV DR MA WN D SG SW KS P PS WS AV T MA LN M N V L L ME A HC CSY T D P R FJ B E E R LS JA J CJ EN JR C M Y

Howland Huber Hung Ikuno Iomdina John Jones Kashchenko Kashyap Kee Khodzhabekyan Khvatova Kostanyan Kruzhkova Kwan Lam Lam Lambrou Lazuk Lee Leverenz Li Lo Lo Logan Mak Mallen Markossian Markossian Martínez Maximova McCollim Mihashi Mirsayafov Mitchell, Mitchell, Moeschberger, Morgan Mutti Nakai Ng Norton Ohji O'Leary Onufriychuk Orbachevsky Oriowo Pandian Panteleeva Payor Phillips Polyakov

14 29 16 46 36 44 22 12 46 25 16 20 50 47 38 30 22, 23 42 22, 23 44, 45 23 25 44 32 11, 12, 13 31 25 30 34 32 13, 22, 35 16 48, 50 20 41 42 44 30 22 10, 11, 12, 13 29, 46 40 30 31, 32 33 37 46 12 11, 39 31 46 19

53

HC A LF Y EN T LA TP P CSY NV NV IA GV WCK CSY TC GN AV SY VR TT KK SCL N YT E GM GA D MV R T DS GL P ML I DO Y PWK TT M DJ ON LS OM A OA RE JR A

19 46 19 41 20, 26, 36 34 11, 39, 50 30 31 19 27, 28 36 20 26 48 13, 35 35 20 20, 26, 36 44 22 19 44, 45 35 12 46 12, 31 28, 29 46 30 26 32 19 34 11, 39, 50 34 11 45 11, 39 49 44, 45 16, 21 41 14, 34, 51 24 26 22 34 46 20 25, 38 29, 46

10th International myopia conference 2004 Potter Qin Radhakrishnan Ramamirtham, Reuter Roorda Rose Rosenblum Ruegg Sankaridurg Sarra Saw Schmid Schmid Seidel Seitkamalovna Siegwart Sivak Slyshalova Smith Spector

JA X H RA KS A K YZ C PR GM SM G KL D KK JT, Jr JG NN EL, III TD

17, 24 33 14, 51 19 50 19 34, 45 24, 30 46 34 46 42 49 13, 20, 35, 38 31, 32 46 16 22 36 15, 16, 19 46

Stone Strang Strang Svyatova Sweeney Tan Tan Tang Tano Tarutta

RA NC NC G DF DTH SB WC Y EP

Tavakoli Taylor Theagarayan Thorn Ting To Trevithick Troilo Tverskaya Uzunyan Valsky Vasserman

M HR B F PWK CH JR D S DG VV N

9, 42 31, 32 24 46 34 42 42 44, 45 41 25, 26, 27, 28, 34, 41, 42, 46 36 44 14, 51 12 13, 35 35 22 12, 17 29, 46 34 27 29

Verzhanskaya Wallace Wallman Ward Whitaker Wolffsohn Woo Wood Yap Yekta

TY KM J B D JS GC I MKH AA

34 20 18 41, 46 24 11, 13 23, 38 23 44, 45, 48 36

Ying Yip Young Yu Zadnik Zhokhov Zolnikova

54

QG SP TL L K SS IV

19 44, 45, 48 43 42 11, 39 20 28

ISBN: 0-907262-67-8

10 th International Myopia conference , Cambridge 2004 - abstract book

Recommend Documents