A) Retinal artery occlusion
Retinal artery occlusion is a type of stroke that affects the eye and is caused by emboli that occlude the arteries. Conditions that may predispose to embolus formation are atrial fibrillation, endocarditis and atherosclerotic disease. Emboli can originate from the heart or the carotids and block small end arteries in the retina.
The most common symptom is acute, painless vision loss (partial or complete) in the affected eye. Retinal artery occlusion causes significant ischemia to the retina with long term complications such as neovascular glaucoma.
Blood workup and imaging studies including echocardiography and Carotid Doppler ultrasonography are necessary to determine the etiology of the artery occlusion.
No specific treatment is available for retinal artery occlusion.
B) Retinal vein occlusion
Retinal vein occlusion (RVO) is a much more common condition than the artery occlusion and one of the commonest causes of vision loss worldwide. It affects usually patients over the age of 60. It is caused by mechanical compression of the vein from a thickened arteriosclerotic artery. This leads to drainage impairment of the venous circulation and subsequent fluid accumulation in the macula.
Symptoms of RVO include sudden or gradual onset of blurred patches in the visual field; patients may be occasionally asymptomatic.
Patients with RVO under 45 years of age need to have extensive blood workup to exclude coagulopathy.
Treatment of RVO includes anti-VEGF injections to treat the macular edema and laser therapy to the ischemic areas of the retina.
