A Man of Singular Vision

Central retinal artery occlusion (CRAO)

The diagnosis must be suspected in any case of sudden painless loss of vision, and is clinched by the appearance of the retina (see Q2).

History:

• sudden and painless loss of vision (seconds)
• Consider underlying causes: emboli, thrombosis, GCA, CTDs, hypercoagualtion, trauma, migraine, syphilis, sickle cell disease, Behcet

Examination:

• Visual acuity — markedly reduced e.g. <6/60
• Marcus-Gunn pupils (RAPD)
• Red reflex — abnormal and asymmetrical
• Fundoscopy — a pale retina with areas of cilioretinal sparing and a classic ‘cherry red spot’ in the macula (may be subtle). Arteriolar and venular narrowing and box-car appearance

CRAO, like chemical injuries to the eyes, is a true ophthalmological emergency.

Urgent ophthalmology referral, and a physician to work up underlying causes:

• Urgent ESR and CRP to exclude GCA.
• TIA and vasculitis work up as per amaurosis fugax

Treatment is unproven but includes:

• immediate ocular massage
• anterior chamber paracentesis
• IOP reduction with acetazolamide (e.g. 500mg IV) or timolol (0.5% topical drops bd)
• Breathe into a paper bag (respiratory acidosis induces retinal vasodilation)

There is no cherry red spot and vision is reduced to light perception. The entire retina is whitened. The treatment is the same.

Branch retinal artery occlusion (BRAO)

There is no cherry red spot and there is only partial visual field loss. A segment of retina is whitened along the distribution of a branch retinal artery. The treatment is the same.

• Ehlers JP, Shah CP, Fenton GL, Hoskins EN. The Wills Eye Manual: Office and Emergency Room Diagnosis and Treatment of Eye Disease Lippincott Williams & Wilkins
• NSW Statewide Opthalmology Service. Eye Emergency Manual — An illustrated Guide. [Free PDF]