The retina of the eye is supplied by a large artery called the central retinal artery, and then drained by a central retinal vein. In certain conditions, either the main artery or vein, or its branches, may become blocked and cause a loss in vision.

Retinal artery occlusions are more uncommon. If the main artery becomes blocked (central retinal artery occlusion), you may suffer severe visual loss. If one of the smaller branches becomes blocked, it is called a branch retinal artery occlusion and you may experience partial vision loss or in some cases, not even realize it. This is often the result of small clots which are released from other parts of the body.

In either case, this is an emergency and immediate treatment is aimed at limiting the area of the retina which is damaged by lack of blood. This may involve using some eyedrops and oral medication and even drawing fluid out of the eye. More importantly, we want to look for a possible source of the clots and will arrange other non-ocular tests so as to lower the risk of this happening again.

Retinal vein occlusions can also happen to the main vein (central retinal vein occlusion) or to one of the draining branches (branch retinal vein occlusion).

This is usually the result of the hardening of the vessels called atherosclerosis, and high blood pressure is one of the main risk factors for this. Other risk factors include smoking, increased age, diabetes, and ocular conditions such as glaucoma.

The main complications that arise from retinal vein occlusions are the growth of abnormal, friable new vessels, like those seen in diabetes that was previously described, as well as swelling at the central part of the retina causing macular edema.

After a thorough clinical examination and imaging tests, treatment can involve a combination of laser treatment and injections of anti-vascular endothelial growth factor agents depending on the severity of the condition.