SECTION
8
Ophthalmology Conjunctivitis
Bilateral
Unilateral
Watery discharge
Purulent, thick discharge
Easily transmissible
Poorly transmissible
Normal vision
Normal vision
Itchy
Not itchy
Preauricular adenopathy
No adenopathy
No specific therapy
Topical antibiotics
.... T IP The "must know" subjects in ophthalmology are: • • • •
The red eye (emergencies) Diabetic retinopathy Artery and vein occlusion Retinal detachment
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Master the Boards: USMLE Step 2 CK
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The Red Eye (Ophthalmologic Emergencies)
Presentation
Itchy eyes, discharge
Autoimmune diseases
Pain
Trauma
Eye findings
Normal pupils
Photophobia
Fixed midpoint pupil
Feels like sand in eyes
Most accurate test
Clinical diagnosis
Slit lamp examination
Tonometry
Fluorescein stain
Best initial therapy
Topical antibiotics Topical steroids
Acetazolamide, mannitol, pilocarpine, laser trabeculoplasty
No specific therapy; patch not clearly beneficial
Glaucoma Chronic Glaucoma
Chronic glaucoma is most often asymptomatic on presentation and is diagnosed by routine screening. Confirmation is with tonometry indicating extremely elevated intraocular pressure. Treat with medications to decrease the production of aqueous humor or to increase its drainage. • Prostaglandin analogues: latanoprost, travoprost, bimatoprost • Topical beta blockers: timolol, carteolol, metipranolol, betaxolol, or levobunolol • Topical carbonic anhydrase inhibitors: dorzolamide, brinzolamide • Alpha-2 agonists: apraclonidine • Pilocarpine • Laser trabeculoplasty: performed if medical therapy is inadequate Acute Angle-Closure Glaucoma
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Look for the sudden onset of an extremely painful, red eye that is hard to palpation. Walking into a dark room can precipitate pain because of pupilary dilation. The cornea is described as "steamy" and the pupil does not react to light because it is stuck. The cup-to-disc ratio is greater than the normal 0.3. The diagnosis is confirmed with tonometry. Treat with: • Intravenous acetazolamide • Intravenous mannitol to act as an osmotic draw of fluid out of the eye • Pilocarpine, beta blockers, and apraclonidine to constrict the pupil and enhance drainage • Laser iridotomy
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Ophthalmology
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Herpes Keratitis Keratitis is an infection of the cornea. The eye may be very red, swollen, and painful, but do not use steroids. Fluorescein staining of the eye helps confirm the dendritic pattern seen on examination. Steroids markedly increase the production of the virus. Treat with oral acyclovir, famciclovir, or valacyclovir. Topical antiherpetic treatment is trifluridine and idoxuridine.
Beware of steroid use for herpes keratitis. Steroids make the condition worse.
Cataracts There is no medical therapy for cataracts. Surgically remove the lens and replace with a new intraocular lens. The new lens may automatically have a bifocal capability. Early cataracts are diagnosed with an ophthalmoscope or slit lamp exam. Advanced cataracts are visible on examination.
Diabetic Retinopathy Annual screening exams should detect retinopathy before serious visual loss has occurred. Nonproliferative or "background" retinopathy is managed by controlling glucose level. The most accurate test is fluorescein angiography. Proliferative retinopathy is treated with laser photocoagulation. Vascular endothelial growth factor inhibitors (VEGF) are injected in some patients to control neovascularization. Vitrectomy may be necessary to remove a vitreal hemorrhage obstructing vision.
Figure 19.1: New blood vessel formation obscures vision. Source: Conrad Fischer, MD.
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Master the Boards: USMLE Step 2 CK
Retinal Artery and Vein Occlusion Both conditions present with the sudden onset of monocular visual loss. You cannot make the diagnosis without retinal examination. There is no conclusive therapy for either condition.
Figure 19. 2: Retinal artery occlusion presents with sudden loss of vision and a pale retina and dark macula. Source: Conrad Fischer, MD.
The maculq,. is described as "cherry red" in artery occlusion because the rest of the retina is pale.
Figure 19.3: Retinal vein occlusion leads to extravasation of blood
into the retina. Source: Conrad Fischer, MD.
Treatment of artery occlusion is attempted with 100% oxygen, ocular massage, acetazolamide, or anterior chamber paracentesis to decrease intraocular pressure, and thrombolytics. Try ranibizumab for vein occlusion.
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Ophthalmology
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Retinal Detachment Risks include trauma to the eye, extreme myopia that changes the shape of the eye, and diabetic retinopathy. Anything that pulls on the retina can detach it. Detachment presents with the sudden onset of painless, unilateral loss of vision that is described as "a curtain coming down." Reattachment is attempted with a number of mechanical methods such as surgery, laser, cryotherapy, and the injection of an expansile gas that pushes the retina back up against the globe of the eye.
Figure 19.4: Sudden, painless loss of vision "like a curtain coming down." Source: Conrad Fischer, MD.
Macular Degeneration Macular degeneration is now the most common cause of blindness in older persons in the United States. The cause is unknown. There is an atrophic (dry) type and a neovascular (wet) type. Visual loss in macular degeneration: • Far more common in older patients • • Normal external appearance of the eye • Loss of central vision Neovascular disease is more rapid and more severe. New vessels grow between the retina and the underlying Bruch membrane. The neovascular or wet type causes 90% of permanent blindness from macular degeneration.
Atrophic macular degeneration has no proven effective therapy.
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Master the Boards: USMLE Step 2 CK
Figure 19.5: Macular degeneration can be diagnosed only by visualization of the retina. Source: Conrad Fischer, MD.
The best initial therapy for neovascular disease is a VEGF inhibitor such as ranibizumab, bevacizumab, or aflibercept. They are injected directly into the vitreous chamber every 4 to 8 weeks. Over 90% of patients will experience a halt of progression, and one-third of patients will have improvement in vision.
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