A Man of Singular Vision

aka Ophthalmology Befuddler 026

A 52 year-old man presents with sudden onset loss of vision in his right eye. He has no other symptoms. His past medical history is notable for hypertension, hyperlipidemia and angina. His medications include aspirin, atenolol, and atorvastatin. He can barely detect hand movements with his right eye and has a relative afferent pupillary defect.

Fundoscopy shows this appearance:

Questions

Q1. What is the likely diagnosis?

Answer and interpretation

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).

Q2. What features on history and examination should be looked for?

Answer and interpretation

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

Q3. What is the investigation and management?

Answer and interpretation

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)

Q4. How does an opthalmic artery occlusion differ from this condition?

Answer and interpretation

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

Now, consider an alternative scenario in which the patient only had partial visual field loss and you saw this on funduscopy:

Q5. What is the diagnosis in this case, and how does it differ from the first?

Answer and interpretation

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.