Branch Retinal Artery Occlusion

Branch retinal artery occlusion is blockage of one branch of the central retinal artery, infarcting the retina in that segment. It accounts for about 38% of acute retinal artery occlusions. It is most often embolic, and the temporal branches are involved more often than the nasal ones.

Embolus types:

• Cholesterol (Hollenhorst plaques): bright yellow, refractile, located at bifurcations, from carotid atheroma
• Calcific: white, non-refractile, from cardiac valves and the aortic root
• Fibrin platelet: gray white, elongated, from diseased vessels

Other causes are vasculitis, giant cell arteritis, hypercoagulable states, sickle cell disease, endocarditis and atrial myxoma. About 80% of eyes recover acuity of 20/40 or better, but the field defect persists. The importance of this condition is its meaning as a marker of embolic stroke and cardiovascular risk.

• Sudden painless sectoral or altitudinal visual field loss in one eye
• Central acuity preserved if the macula is spared
• Retinal whitening confined to the territory of the occluded branch, with a visible embolus in many cases
• Arteriolar narrowing and segmentation downstream
• Relative afferent pupillary defect only when the defect is large
• Amaurosis fugax preceding the event in some patients
• Neurological symptoms (weakness, speech disturbance) suggest concurrent cerebral emboli

• Dilated fundus examination identifies segmental whitening and any embolus.
• Automated perimetry maps the defect.
• OCT: inner retinal hyperreflectivity and thickening in the acute phase, atrophy later. Fluorescein angiography shows delayed filling of the affected branch.
• Urgent ESR, CRP and platelets in anyone over 50, to exclude giant cell arteritis.
• Carotid duplex or CT/MR angiography, ECG, 24 to 72 hour rhythm monitoring, transthoracic echocardiography with transesophageal study when a cardiac source is suspected.
• Blood tests: glucose, HbA1c, lipids, full blood count, clotting. In patients under 50, thrombophilia, autoimmune screen and syphilis serology.
• MRI brain with diffusion weighted imaging for silent infarcts.

Differentials: cilioretinal artery occlusion, branch retinal vein occlusion, cotton wool spots from hypertension or diabetes, retinal detachment, optic neuropathy.

There is no proven treatment to restore the occluded branch. Management centres on the embolic source and stroke prevention, and the patient is managed on the transient ischemic attack pathway.

• Aspirin 300 mg once daily for 2 weeks, then clopidogrel 75 mg once daily long term.
• Atorvastatin 80 mg at night, LDL target below 1.8 mmol/L (70 mg/dL).
• Blood pressure target below 130/80 mmHg. Treat diabetes and stop smoking.
• Carotid endarterectomy within 2 weeks for symptomatic stenosis of 70 to 99% (50 to 69% in selected patients).
• Atrial fibrillation: apixaban 5 mg twice daily (2.5 mg twice daily if two of: age 80 or above, weight 60 kg or below, creatinine 133 micromol/L or above).
• Giant cell arteritis: methylprednisolone 1 g IV daily for 3 days, then prednisolone 1 mg/kg/day orally (maximum 60 to 80 mg) tapering over 12 to 24 months, with omeprazole 20 mg daily, calcium 1000 mg, vitamin D 800 IU daily and alendronate 70 mg weekly.
• Endocarditis: blood cultures before antibiotics and cardiology review. Cardiac myxoma needs surgical resection.
• Ocular massage and paracentesis give no clear benefit in branch occlusion and are reserved for presentations within hours with a large macular threatening territory.

Neovascularization after branch artery occlusion is uncommon. Review at 4 to 6 weeks, repeat perimetry and OCT at 3 months, and examine for retinal neovascularization if a large area is nonperfused. Counsel the patient on stroke symptoms and cardiovascular risk modification. The risk of a second embolic event is highest in the first weeks.