MOTILITY,

Ocular Motility/Binocular Vision Eva Lindahl C.O.M.T. Types of Deviations Eso - in Exo - out Hyper - up Hypo - down Phoria - a latent tendency of eyes to deviate that is prevented by fusion. A deviation occurs only when a cover is placed over an eye; when uncovered, the eye straightens (heterophoria) Tropia - eye misalignment caused by extraocular muscle imbalance; one fovea is not directed at same object as the other. Deviation is present present even when both eyes are uncovered (heterotropia) X, E, H - phoria XT, ET, HT - manifest

Muscle Abbrev. Medial Rectus MR Lateral Rectus LR Superior Rectus SR

Inferior Rectus

IR

Superior Oblique

SO

Inferior Oblique

IO

XT, ET - stronger tropia than phoria X(T), E(T), H(T) - intermittent

Main Actions Adduction Abduction Elevation intortion Adduction Depression Extortion Adduction Intortion Depression Abduction Extortion Elevation Abduction

Cranial N III VI III

Testing Position straight nasal straight temporal up and temporal

III

down and temporal

IV

down and nasal

III

up and nasal

Abduction - monocular movement of an eye outward (away from the nose) Abnormal/Anomalous Retinal Correspondence (ARC) - adaptation to compensate for a long-standing eye deviation; fovea of the straight (non-deviated) eye and a non-foveal retinal point of the deviated eye work  together, sometimes permitting single binocular vision despite misalignment of the eyes. Criteria for ARC: 1. Patient must have manifest esotropia (monocular or alternating) - hardly ever exo 2. Must be the same amount of crossing all the time (no accommodation) 3. The patient has the desire to fuse, but because of manifest deviation is unable to do so. If he fuses, it is abnormal. 4. May or may not have amblyopia convergence/accommodation ratio) - numerical expression for relationship between AC/A ratio (accommodative convergence/accommodation the amount both eyes simultaneously turn inward (converge) and the amount their lenses increase in power (accommodate). In normal individuals individuals this ratio averages 5:1. Accommodative convergence is expressed in prism diopters ( ∆), and accommodation is expressed in diopters (D). Distance-near Distance-nea r method : AC/A = 1/3 (n ∆-d∆) + interpupillary interpupillary distance (in cm) (Wilson p 121) n∆ = near deviation d∆ = primary position deviation

Accommodation - increase in optical power by the eye to maintain a clear image (focus) as objects are moved closer. Accommodative convergence - that portion of the range of inward rotation (toward nose) of both eyes that occurs in response to an increase in optical power for focusing (accommodation) by the eyes' lenses. Accommodative esotropia - excessive turning of an eye inward (toward nose) caused by an overactive convergence response to the accommodative accommodative effort necessary to keep vision clear. Eyeglass correction for the hyperopia relaxes accommodation, accommodation, allowing eyes to remain properly aligned. Sometimes bifocals are are necessary to correct excessive inturning at near. Adduction - monocular movement of an eye inward (toward the nose). horizontal deviation. With the opposite eye occluded, the Afterimage Test - evaluates retinal correspondence in a horizontal macula of each eye is marked with an afterimage using a linear light flash with the fixation point blocked. Horizontal orientation is used OD, vertical OS. Then the patient reports the composite binocular image image perceived (eyes open or closed). • Interpretation: NRC: NRC: a symmetrical cross with a central area void of an afterimage esotropic ARC: ARC: a vertical line asymmetrically displaced to the right in a crossed fashion exotropic ARC: ARC: a vertical line asymmetrically displaced to the left in an uncrossed fashion Agonist, primary mover - extraocular muscle mainly responsible for moving eye into desired position. Alternating - a deviation which can be encouraged to hold fixation with either eye. Alternate Cover Test - measures the entire deviation (tropia (tropia plus phoria). Test in all appropriate positions of gaze to explore for incomitance. Amblyopia, Amblyopia, ("lazy eye") - decreased vision (two lines of vision or more) in one or both eyes without detectable anatomic damage in the eye or visual pathways. Uncorrectable by optical means (e.g., eyeglasses). eyeglasses). Including strabismic, anisometropic, refractive, ex anopsia. Amblyopia Ex Anopsia, amblyopia of disuse - reduction of vision from not seeing or disuse Angle Kappa - the angle between the visual axes and the anatomic (pupillary) axes. axes. Can be positive positive or negative. A slightly positive angle kappa is physiologic due to usual foveal positioning temporal to the anatomic axis. • If positive If positive,, the pupillary reflex will be seen on the nasal side of the midline. (Exo ( Exo type of deviation). • If negative If negative,, the pupillary reflex will be seen to the temporal side of the midline (Eso ( Eso type of deviation). • Use the cover - uncover test to distinguish if deviation is pseudo. Antagonist - extraocular muscle whose action opposes that of the contracting muscle (agonist) that moves the eye. Contralateral - extraocular muscle on the fellow eye whose action

opposes the action of a contracting muscle of an eye (e.g., RSR and LSO) Ipsilateral - extraocular muscle whose action opposes the action of another muscle on the same eye (e.g., MR and LR) A/V Patterns - eye deviations in which the deviation is more pronounced in the up or down gaze. A pattern - more convergent in upgaze or divergent in downgaze (10 P.D. difference necessary) • Either more eso up or more exo down V pattern - more convergent in downgaze or divergent in upgaze (15 P.D. difference necessary) • Either more eso down or more exo up used for evaluating retinal correspondence. The lenses are placed with Bagolini lenses - finely striated clear lenses used the best correction in a trial frame in a manner such that the light streak produced by viewing the target light is oriented at 135° OD and 45° OS. The patient views a white fixation light at 20 ft or 13 in. under normal room lighting. • Interpretation: NRC (orthotropia, central fusion) = 2 light streaks crossing at a light without a break in either line. strabismus > 9 ∆with NRC = 2 separated light streaks, each passing through its own light in either a crossed (exotropic) or uncrossed (esotropic) manner strabismus > 9 ∆ with ARC = 2 light streaks crossing at a light with either a 5° to 6° break in one line (esotropia) or a much larger break in one line (exotropia) absence of binocular vision = one light streak passing through a light Bielschowsky Three Step Test (B3ST) - a test which helps isolate which of the eight cyclovertical muscles may be at fault in a vertical muscle palsy Step 1: 1: Determine the presence of a RHT or LHT in the primary position. Step 2: 2: Determine if the HT is larger in right or left gaze Step 3: 3: Determine if the HT is larger when measured during head tilt to the right or left. (See attached worksheet) Binocular vision, single binocular vision blending of separate images seen by each eye into one composite image Blowout fracture - break of bony orbital floor or walls caused by blunt trauma to eye or orbit; intraorbital contents are pushed into one or more of the nasal sinuses Both Eyes - OU, Oculus Uterque Brown's syndrome - sheath of superior oblique muscle that does not, or cannot, relax when the eye attempts to look upward and inward, mimicking a palsy of the inferior oblique muscle. muscle. Unilateral; may be congenital or acquired. Comitant (Concomitant) - eye misalignment in which the amount of deviation remains the same in every direction of gaze Confusion - erroneous perception that two different objects occupy the same position in space. Short term, leads to suppression. Conjugate movement - parallel movement of  both eyes in same direction of gaze

Convergence - simultaneous inward movement of both eyes (toward each other) usually in an effort to maintain single binocular vision as an object approaches Convergence amplitudes - amount, in prism diopters, that the eyes can simultaneously turn inward (toward nose) before double vision ensues Convergence insufficiency - eye muscle problem in which the eyes cannot be pulled sufficiently inward (toward nose) to maintain single vision when attempting attempting to fixate on a near object. Characterized by eye fatigue or double vision. Corneal Light Reflex Tests - general tests of muscle deviation by approximating the displacement of the corneal light reflex in the nonfixating nonfixating eye. Including the Hirschberg Hirschberg and Krimsky Tests. See Quantitative Diagnosis of Strabismus. binocularity by covering one eye. Look for movement of one Cover - Uncover Test - monocular test, interrupting binocularity eye or other. Do 2 - 3 times. Determines: type type of deviation (tropia, phoria), phoria), direction of deviation (eso, exo), alternating or monocular, constant or intermittent, intermittent, preferred eye, fixation pattern, pattern, nystagmus. Done wearing full correction at 20 ft., the patient fixates on a target slightly slightly above the acuity threshold. For near, fixates at an accommodative target (letters) at 16". • tropia - Cover test - opposite eye moves to fixate when covered • phoria - Uncover test - same eye moves to to fixate as uncovered for hyperopes - done cc and sc for patients with bifocals - done c and s bifocals for patients with vertical deviations - 3° positions and head tilt (remember to position the prism parallel to the floor of the patients orbit, not the floor of  the room) for patients with head turn to R or L, measure R and L gaze before up and down for patients with chin up or down position, measure up and down gaze before R or L for patients with ET ET,, measure down before up XT, measure up before down for patients with XT, Cranial Nerve Innervation # 3. Oculomotor SR, MR, IR, IO, levator, pupil constriction # 4. Trochlear SO # 6. Abducens LR Depressor - muscle which moves the eyeball downward, IR, SO Deviation - misalignment of eyes caused by extraocular muscle imbalance: one fovea is not directed at the same object as the other. Differential diagnosis - the thought process that leads an examiner through the exam to a final diagnosis through a process of  elimination. The history provides clues, clues, the examination tests tests to either prove or disprove the tentative diagnosis. Diplopia - erroneous perception that the same object occupies two different positions in space. Homonymous Diplopia (uncrossed) - seen when a patient has esotropia. A nasal retinal element element is stimulated and is projected temporally. temporally. The greater the deviation, the greater the disparity disparity of images. element is stimulated and the Heteronymous Diplopia (crossed) - seen in exotropia. A temporal retinal element image is projected nasally. Paradoxic Diplopia - double vision, with unexpected spatial localization of images relative to the actual position of the eyes. Usually found after strabismus strabismus surgery; caused by the presence of abnormal retinal correspondence. (Incorrect diplopia for the type of deviation i.e., eso - heteronymous, or exo - homonymous). Diplopia Fields - any visual field done to show areas of single and double vision. Dissociated vertical deviation (DVD) - either eye elevates under cover occlusion, yet never drops below the midline. Generally asymmetrical asymmetrical and and unilateral. Simulates an IO overaction, except when occluded while abducted will elevate. elevate. Overactive IO will will not. Divergence - eyes that simultaneously rotate outward (away from each other), usually in an effort to maintain single binocular vision. Divergence amplitudes - amount both eyes can simultaneously rotate outward (away from each other) before inducing double vision. vision. Measured in prism diopters.

Divergence excess - type of outward deviation (exotropia) that is greater when the target is at a distance (20 ft) than at near (16 in). Divergence insufficiency - type of inward deviation (esotropia) that exists only for distances beyond about 5 feet. Dominant eye - preferred eye for sighting. The eye that leads and controls the other during binocular eye movements. Usually on same side of body as dominant hand. Double Maddox Rod - useful for quantitation of a cyclodeviation. A red horizontal line is formed OD with a red Moddox rod while a white ho rizontal line is formed OS with a clear Maddox rod. If the two lines are not parallel, the patient neutralizes the deviation by turning the red Maddox rod until the red line is parallel and the corresponding degrees of correction are read off the trial frame. Duane's Classification of Horizontal Strabismus: Convergence insufficiency - exo is greater at near than in the distance Convergence excess - eso is greater at near than distance Divergence excess - exo is greater in the distance than at near Divergence insufficiency - eso is greater in the distance than at near •(All horizontal strabismus is one of these except accommodative esotropia) Duane's retraction syndrome - narrowing of the lid fissure and glove retraction during attempted adduction. Additionally: Type 1 - decreased abduction Type 2 - decreased adduction Type 3 - both decreased abduction and adduction positions of the eye. Done with pursuit movements in Ductions - monocular rotations of the eye in six diagnostic positions the diagnostic positions with a muscle light or penlight. abduction – out adduction - in supraduction - up infraduction - down incycloduction - tortional rotation of 12 o'clock meridian toward the nose excycloduction- tortional rotation of 12 o'clock meridian toward the temple Eccentric fixation - visual abnormality in which a retinal area other than the fovea is used for visual fixation. fixation. Occurs as an adaptive mechanism mechanism of some patients with amblyopia or when the fovea has been destroyed by some pathologic process. The patient has amblyopia. amblyopia. The eye still fixates fixates eccentrically (turns) when the other eye is covered. covered. Always monocular. monocular. Elevator - muscle which moves the eye upward, SR, IO. pseudostrabismus, infantile and congenital Esodeviations - deviations where the eye turns inward. Including, pseudostrabismus, esotropia, accommodative esotropia, monofixational syndrome, acquired esotropia, consecutive (after muscle surgery) esotropia, 6th nerve (LR) palsy, divergence paralysis, strabismus fixus, Duane's retraction syndrome Etiology - causes of a disease or abnormal condition Excycloduction, extortion - tortional rotation of 12 o'clock meridian away from the nose exotropia, Exodeviations - deviations where the eye turns outward. Including pseudoexotropia, congenital exotropia, divergence excess, MR (3rd nerve) palsy, uniocular blindness, consecutive (after muscle surgery), convergence insufficiency, infantile XT, Duane's type 2.

Fixation Reflex (CSM) - tests the ability to fixate and follow a light source in a central, steady, and maintained manner (birth to 2 1/2 years) Forced duction test - mechanical rotation of eyeball to determine presence of any mechanical restrictions to movement; anesthetized conjunctiva and episclera at the cornea scleral junction (limbus) are grasped with forceps, and the eyeball is forcible moved into different positions. Positive - resistance, negative - moves freely. Four Diopter Base-Out Prism Test - tests for fusion or suppression in a minimally deviated eye; a 4-prism-diopter prism is held base-out in front of eye while patient fixates fixates on a light. Absence of convergence movement indicates suppression. Positive - suppression, suppression, negative - fusion. Fovea - central pit in the macula that produces sharpest vision; contains a high concentration of cones and no retinal blood vessels Fresnel prism (freh-NEL) - series of flexible plastic lenses with smooth adhesive side that enables them to adhere to eyeglass lenses. Used for correcting eye eye deviations or refractive refractive errors. Fusion - ability to blend two similar images into one Fusion potential - using prisms to neutralize deviation, then testing fusion Fusional amplitudes - amount the eyes can simultaneously move inward (converge) added to the amount they can simultaneously move outward outward (diverge), while maintaining single vision. vision. Measured by increasing BO, BI, BU or BD prisms and measured at distance (20 ft) and near (13 in) using a Risley rotary prism or prism bar. Distance divergence - use 20/40 letters, add larger BI prism until break point (patient sees double), then less prism until recovery (fuses again). Results are recorded recorded as break/recovery Near divergence - same as distance BI with near accom. target Distance convergence - record "blur", break, and recovery pt, and (when blurring occurs = accommodative conv, not fusional convergence)(a normal patient may have fusional convergence measurements of 18/14) using a BO prism. Near convergence - same as distance BO with near accom. target *(near usually = 2X distance, convergence usually = 2X divergence) *(recovery usually = 1 notch down prism bar from break point) Jump convergence = largest BO prism that can be immediately immediately overcome (usually same as recovery point) • base-down OD for positive vertical vergence • base-up OD for negative vertical vergence thyroid-related hormone concentration. Includes eyelid Graves' disease - eye signs that may occur with excessive thyroid-related retraction, eyelid lag on downward gaze, corneal drying, eye bulging (proptosis), fibrotic extraocular muscles, and optic nerve inflammation Harmonious ARC - Binocular adaptation of the retinas to a long-standing eye deviation. deviation. Fovea of the straight (non-deviated) eye and a non-foveal point of the deviated eye (that corresponds to the deviation) work  together permitting poor quality, single binocular vision.. Hering's Law of Motor Correspondence - (law of equal innervation), Innervation to one extraocular muscle to contract generates an equal innervation to contract its yoke muscle (that muscle performing performing the same function in the other eye). eye). For example, RLR and LMR. Hess Screen - similar to the Lanaster Red-Green Test, except many fixed lights are illuminated by the examiner sequentially at a testing distance of 0.5 m. Heteronymous diplopia - crossed diplopia, located on the opposite side Homonymous diplopia - uncrossed diplopia, located on the same side Horopter - the imaginary arc formed by the group of points in space that fall on corresponding retinal points in each eye which are therefore seen singly H2S - mnemonic: Hering's law (H) applies to innervation of extraocular muscles of both (2) eyes while Sherrington's law (S) refers to innervation of extraocular muscles in one (1) eye. See

varies in amount depending on the direction of gaze. Can be due to Incomitant (noncomitant) - deviation that varies EOM paresis, Cranial nerve palsy, or restrictive strabismus Incycloduction, intortion - tortional rotation of 12 o'clock toward the nose Innervation - nerves giving stimulus to muscles (LR-6, SO-4, the rest are 3) Lancaster Red - Green Test - a red-green sensory motor test to create a graphic representation of the incomitance of a strabismic deviation in the various various positions of gaze. The patient wears dissociating red-green glasses. glasses. The eye with the red lens perceives only red targets on a visual field screen, and the eye with the green lens perceives only a projected green pointer that the patient is requested to superimpose on red targets in the visual field. Goggles are reversed to compare compare primary and secondary secondary deviations. The testing distance is is 2 m. Latent deviation - a deviation that is only apparent when fusion is broken Left eye - OS, oculus sinister Macula - small area in the retina surrounding the fovea Maddox Rod - dissociating test to provide vertical or horizontal line type image by the eye that has the rod in front of if. Easily dissociates both eyes but does not differentiate differentiate between phorias and tropias. . If red line is centered through the white white light, no deviation is present. The image is seen opposite where the eye is looking. Test is done D (20 ft) and N (13 in), in a dark room. The patient is instructed instructed to "look at the white white light and tell where the red line is" uncrossed diplopia = eso crossed diplopia = exo Manifest deviation - one that is present at all times turns in or out constantly. Will not hold fixation with Monocular - one eye turns other eye unless good eye is covered Monocular diplopia - multiple images images seen with one eye. Commonly caused by early cataract or irregular cornea Motility - study of extraocular muscles ad their effect on eye movements Near Point of Convergence (NPC)(NPC) - a small target stimulating accommodation is moved along the midline toward the patient until a break point, and back until recovery of fusion. fusion. A receded NPC can indicate convergence convergence insufficiency. Normal retinal correspondence - binocular condition in which both foveas work together as corresponding retinal points, with resultant images blended (fused) in the occipital cortex of  the brain. Nystagmus - involuntary, rhythmic side-to-side or up and down (oscillating) eye movements that are faster in one direction than the other. Use alternate forms of occlusion (+6.00 - +10.00 trial lens) if there there is any nystagmus. Objective angle - the actual measurement of the patient's eye turn Occlusion - covering of the eye by an opaque membrane (patch) Orthophoric - absence of eye deviation (or tendency toward deviation); no ocular movement is elicited by covering an eye while other eye views a visual target. Orthoptics - study and treatment of defective eye coordination, binocular vision, or functional amblyopia by non-surgical methods, e.g., glasses, prisms, or exercises. Results in improved improved comfort and efficiency efficiency of binocular function. Panum's fusional space - zone immediately to front and back of fixation object, in which single binocular vision with depth perception is possible. Outside this area, diplopia occurs. Paralysis, palsy - complete or partial loss of muscle function, usually due to nerve damage. In paralytic deviations deviations with face turns, the nose points points toward the direction of gaze in which the palsied muscle is supposed to work. Paretic, paresis -extraocular muscle weakened by damaged nerve supply, which needs more than usual amount in innervation to perform its normal function. Physiological diplopia

- normal binocular function. Fixing on a near object, the distant object is seen uncrossed (homonymous); fixing on a distant object, near object is seen crossed (heteronymous) Positions of Gaze: Gaze : Nine Diagnostic Positions - primary, secondary and tertiary (oblique) positions (30° horizontal and 30° vertical from primary) Six Cardinal Positions - the six diagnostic positions of  gaze in which one of the six "yoked" muscles in each eye is primarily responsible responsible for the eye's rotation. Left gaze, right gaze, and the four tertiary positions of gaze. Near Position - primary position with a near fixation target and 13 in. Bielschowsky positions - 30° left or 30° right head tilt Preferential Looking (PL) - tests the ability to prefer to fixate on a grid requiring a calibrated degree of visual discrimination Preferred eye - eye that takes up fixation Primary deviation - amount of deviation found when an extraocular muscle has been paralyzed and the normal eye is used for fixation. Is always less than the secondary deviation Prism - transparent triangular wedge that bends, but does not focus, light rays toward the position of its base. A one ∆ prism deflects a ray of light at an angle corresponding to 1 cm displacement at a distance 1 m from the prism. 1° (arc degree) of deviation = 1.7 prism diopters. diopters. Measure objectively (what you see) and and subjectively (what the patient says). says). The eye does not move, only the incidence of light or the reflex. • The point of the prism prism goes in the direction direction of the deviation. Use: ET - base out (BO) (either eye) XT - BI HT - BD (on high eye) or BU (on low eye) Hypo – BU • Image is seen toward the apex. apex. light base. • Incidence of light of  is seen toward the base. Prism and Cover Test - doesn't work on restrictive strabismus (Graves', etc.) Use 20/40 or smaller for distance fixation Pseudostrabismus - large epicanthal folds in young children which simulate simulate an eso type of deviation. Coveruncover testing gives a differential diagnosis. Quantitative Diagnosis of Strabismus - Three ways of measuring muscle imbalance: Hirschberg, Krimsky, and Alternate prism and cover test. 1. Hirschberg - least accurate. accurate. Using gross observation observation when the patient is fixating on a penlight at 33 cm or 12". Not very accurate because pupils may be of different sizes. Used with very young children, or patients who can't fixate. pupillary margin =15° = 15° = 30 ∆ between pupil and limbus = 30° = 60 ∆ limbus = 45° = 90 ∆ 2. Krimsky - next most accurate. accurate. Use penlight at 33 cm. cm. Neutralize reflex with a prism used either either base in, out, up or down, depending on deviation. Increase amount of prism until pupillary pupillary reflex recenters. 3. Alternate Prism and Cover Test - most accurate. The prism is placed on the deviating eye. The good eye is covered. The cover is switched. switched. This determines determines the amount of deviation. Recession - a surgical weakening procedure for overactive muscles Red Filter/Red Glass Test - Method of testing for diplopia, diplopia, fusion and ARC vs NRC. The red filter is placed placed over the right eye. The targets are a white fixation light at 20 ft and 13 in. Responses: 1 white - OD suppression 1 red - OS suppression 1 pink = fusion 2 uncrossed (homonymous) = esotropic diplopia 2 crossed (heteronymous) exotropic diplopia 2 vertically separated = vertical diplopia

Resection - a surgical strengthening procedure for weak muscles Restrictive strabismus - eye deviations caused by mechanical obstructions in the orbit involving extraocular muscles; prevents free eyeball movements (blowout fracture, Brown's syndrome, Duane's syndrome, Graves' disease) stimulate both eyes, Retinal Correspondence - relationship between retinas in two eyes. Images from one object stimulate which transmit the information to the brain, permitting a single visual impression localized in the same direction in space. • Normal NRC Homonymous - Eso (uncrossed) • Normal NRC Heteronymous - Exo (crossed) (rare) Abnormal ARC (paradoxic) - Homonymous - Exo Abnormal ARC(paradoxic) ARC(paradoxic) - Heteronymous - Eso Right eye - OD, oculus dexter Secondary deviation - amount of deviation found when an extraocular muscle has been paralyzed and eye with that muscles is used for fixation. Is always greater than primary primary deviation Sherrington's law of Reciprocal Innervation - as one extraocular muscle receives an impulse from the brain to contract, its opposing muscle (direct antagonist) in the same eye receives an impulse to relax. Simultaneous perception - perception of two images simultaneously (one formed on each retina) that are not necessarily superimposed. Simultaneous Prism and Cover Test (S P + C)- used to identify microtropias. The fixating eye is covered covered with an occluder while simultaneously covering the tropic eye with a prism. (Only measures the tropia that is normally manifest) Single Binocular Vision - ability to use corresponding points of the two retinas simultaneously to obtain a single, clear image Spiral of Tillaux – distance in mm of four rectus muscles from limbus to insertion. Stereoacuity Test (Titmus Stereo Test) - to evaluate sensory fusion. Done at 16" with reading illumination and special polarized spectacles. Bifoveal stereopsis > 67 seconds of arc. If  turned 90° has no stereo effect (can use to document malingerers) • fly = 6000 sec of arc • animal line A = 400 sec of arc • animal line B = 200 sec of arc • animal line C = 100 sec of arc • circles 1 - 6 = 800 - 80 sec of arc • circles 7 - 9 = 60 - 40 sec of arc Also: Random dot E (RDE) (near) AO distance vectograph slide (c polaroid glasses) (also tests suppression) Pencil point to pencil point test Stereopsis - blending of two similar but not identical images (one falling on each retina) into one, with resulting three-dimensional perception. imbalance: one fovea is not directed at same object as Strabismus - eye misalignment caused by extraocular muscle imbalance: the other. Can be comitant (no muscle paralysis-same paralysis-same in all directions directions of gaze) or incomitant (muscle paralysis-amount of deviation varies in positions of gaze) Subjective angle - the eye position where the patient indicates fusion occurs transmitted by one eye is ignored to avoid diplopia. Occurs in childhood. Suppression - the retinal image transmitted Synergist - extraocular muscle that assists primary muscle in same eye for making a particular eye movement 25 ∆Base In Test Unharmonious ARC - Binocular adaptation to a long-standing eye deviation. Fovea of the straight (non-deviating) eye and a non-foveal point of the deviated eye work together.

Vectograph - Test chart or picture composed of two polarized images that can be separated visually when viewed with polarized glasses, allowing each eye to see letters or figures that are invisible to the other. For measuring stereo acuity (e.g., Titmus chart) and testing visual acuity. Vergences - disjugate movement, simultaneous movement of both eyes in opposite directions (toward or away from each other, or one up and one down), to obtain or maintain single binocular vision (ex: convergence, divergence) convergence convergence - toward the midline (nose) divergence divergence - away from the midline positive or negative vertical divergence one eye up, one eye down incyclovergence incyclovergence - tortional rotation toward nose excyclovergence excyclovergence - tortional rotation toward temple Versions - conjugate movement, simultaneous simultaneous parallel movement of both both eyes in the same direction. Version testing assesses how well a pair of yoke muscles work  together. dextroversion dextroversion - right levoversion levoversion - left supraversion supraversion - up infraversion infraversion - down dextrocycloversion dextrocycloversion - tortional rotation of 12 o'clock  meridian to right levocycloversion levocycloversion - tortional rotation of 12 o'clock  meridian to left Visual acuity - sharpest point of vision Preferential looking - birth to 2 1/2 Allen pictures - age 2 1/2 to 4 years Illiterate E's - 4 to 5 1/2 years Snellen - > 5 1/2 years • Record which test and if full line presentation was used • If nystagmus is noted, use +6 D to + 10 D lens to "occlude" the other eye Worth 4 Dot - gross test in determining fusion ability (also tests suppression and diplopia). Four lights ( one red, two green, and one white) viewed at 20 ft. Or a flashlight viewed at 13 in. The patient wears red/green red/green filtering lenses (red OD, green OS) over the best spectacle spectacle correction. The red lens filters out green lights (sees red), the green lens filters out red light, the white light is red when OD fixates, green when OS fixates, and alternating red and green with retinal rivalry. Possible sensory perceptions: 2 red = suppression (OS) 3 green = suppression (OD) 3 (2 red/1 green) = suppression (OS) 3 alternating with 2 = alternate suppression 4 total = Worth 4-dot fusion 5 total = diplopia Worth's Three Grades of Fusion 1st grade - superimposition of dissimilar dissimilar images - (simultaneous (simultaneous macular perception). Tested with Maddox rod or haploscope (lion and cage, etc.) simultaneous foveal perception. True fusion. Tested with similar images 2nd grade - motor fusion - simultaneous assessing vergence amplitudes (prism bar or Risley prism)

3rd grade - stereopsis - blending of slightly dissimilar images from two eyes with the perception of depth Yoke muscle - the pair or extra-ocular muscles (one in each eye) which work as a team

Examining The Motility Patient Order of Examination (General Guidelines) ( Stereo test, Random dot E, Worth 4 Dot) Fusion-subjective Fusion-subjective (Stereo Dot) ( test before: removing glasses, VA, versions, red filter, MR or W4D)) 4 ∆ Diopter Base Out Prism test (suppression) or W4D Fusional Amplitudes Distance divergence BI prism until break (use 20/40 letter) Near divergence BI prism until break  Distance convergence BO prism until blur Near convergence BO prism until blur • Always test distance before near, and divergence before convergence • near usually = twice distance, convergence usually = twice divergence Cover-uncover test (determines tropia or phoria) • distance and near Alternate cover test (cross cover) (determines direction of deviation) • Movement of less than 5° (10 ∆) is normal in alternate cover) Prism and cover test (measures amount of deviation) • Do eyes simultaneously if tropic Prism and Cover Test (P + C) Simultaneous Prism and Cover Test (S P + C) Maddox Rod Double Maddox Rod Hess Screen/Lancaster Red-Green Test Diplopia Fields Bielschowsky Three Step Test (B3ST) Versions (two eyes) Ductions (one eye) Visual Acuity Refraction Manifest (without dilating or cycloplegic drops) Cycloplegic (with drops)