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OP16 Ophthalmology
Cornea Toronto Notes 2019
• mayhaveanteriorchambercellsandflare,cornealinfiltrate,scleralthinning,scleraledema
• scleramayhaveapurpleor“violaceous”hue(bestseeninnaturallight),duetorearrangedscleralfibres • failuretoblanchwithtopicalphenylephrine
Treatment
• vision threatening – needs to be referred to ophthalmology
• life threatening- indicator of poor systemic disease control with an increased 5 year mortality rate (not
from scleritis) without treatment of underlying untreated or unrecognized autoimmune condition • systemicNSAIDs,systemicsteroid,andsystemicimmunomodulation
• treatunderlyingetiology
Cornea
• function
■ transmission of light
■ refraction of light (2/3 of total refractive power of eye) ■ barrier against infection, foreign bodies
• transparency due to avascularity, uniform collagen structure and deturgescence (relative dehydration) • 5layers(anteriortoposterior):epithelium,Bowman’slayer,stroma,Descemet’smembrane,andthe
endothelium (dehydrates the cornea; dysfunction leads to corneal edema). Some have argued the
existence of a 6th layer, “Dua’s layer”, although it is debated if this is a truly unique and additional layer • extensivesensoryfibrenetwork(V1distribution);therefore,abrasionsareverypainful
Foreign Body
• foreignmaterialinoroncornea
• mayhaveassociatedrustringifmetallic
• patientsmaynotepain,tearing,photophobia,foreignbodysensation,andredeye
• signsincludeforeignbody,conjunctivalinjection,epithelialdefectthatstainswithfluorescein,corneal
edema, and anterior chamber cells/flare
Complications
• abrasion,infection,ulcer,scarring,rustring,secondaryiritis
Learn the Layers of the Cornea ABCDE
Anterior epithelium
Bowman’s Membrane
Corneal Stroma
Dua’s Layer, Descemet’s Membrane Endothelium
Foreign body behind lid may cause multiple vertical corneal epithelial abrasions due to blinking
Topical analgesics should only be used to
facilitate examination. They should NEVER be Treatment
used as treatment for any ocular problem
Corneal abrasions from organic matter (e.g. twig, finger nail, etc.) have higher recurrence, even years later
Patching for Corneal Abrasion
Cochrane Database Syst Rev 2016; 7:CD004764. Results: 12 RCTs/Quasi-RCTs identified, n=1080. At 24 hours: people receiving patch were less likely to have a healed abrasion (RR 0.89, 95% CI 0.79- 1.00). At 48 hours: similar effect for both groups (RR 0.97, 95% CI 0.91-1.02). At 72 hours: similar effect for both groups (RR 1.01, 95% CI 0.97-1.05) Summary: Certainty of evidence is moderate to low; more research is needed with better quality trials to examine effectiveness of patching for large abrasions. Participants with patch were more likely to receive additional adjuvant treatment and took slightly longer to heal, but the difference was small and possibly clinically insignificant.
• removeundermagnificationusinglocalanestheticandsterileneedleorrefertoophthalmologyfor removal under magnification (depending on depth and location)
• treataspercornealabrasion
Corneal Abrasion
• epithelialdefectusuallyduetotrauma(e.g.fingernails,paper,twigs),contactlens(Figure14) Clinical Features (Table 7)
• pain, redness, tearing, photophobia, foreign body sensation
• de-epithelializedareastainswithfluoresceindye
• painrelievedwithtopicalanesthetic(DONOTusefortreatment-riskofcornealmeltorinfection)
Complications
• infection, ulceration, recurrent erosion, secondary iritis
Treatment
• topicalantibiotic(dropsorointment),abrasionfromorganicmaterialshouldbecoveredagainst
Pseudomonas
• consider topical NSAIDs (caution due to risk of corneal melt with prolonged use), cycloplegic (relieves pain and photophobia by paralyzing ciliary muscle), patch
• mostabrasionsclearspontaneouslywithin24-48h
Recurrent Erosions
• recurrent episodes of pain, photophobia, foreign body sensation with a spontaneous corneal epithelial defect
• usuallyoccursuponawakening
• associatedwithimproperadherenceofepithelialcellstotheunderlyingbasementmembrane
Etiology
• previoustraumaticcornealabrasion • cornealdystrophy
• idiopathic