Retinal Vein Occlusion: Cause and Treatment.

Two Different Forms of Blockage.

Retinal vein occlusion is a relatively common cause of vision loss. The condition takes two forms: branch retinal vein occlusion and central retinal vein occlusion. Despite some similarities, these two conditions differ in terms of risk factors, treatment and visual prognosis.

Branch Retinal Vein Occlusion

What you need to know.
The retinal artery supplies blood to the retina. The blood flows through retinal arterioles, capillaries, and finally through branch retinal veins that drain into the central retinal vein. A branch retinal vein occlusion happens when part of this branch vein system is blocked. A blockage causes backpressure and leads to hemorrhage, exudation, and/or decreased blood flow in the area of the retina drained by that particular branch retinal vein.

How does branch retinal vein occlusion affect vision?

Branch retinal vein occlusion can affect the vision in a number of ways. Poor blood flow (ischemia) through the center of the retina (macula) can severely limit vision. Additionally, exudation and bleeding from the capillaries can cause swelling in the macula (called macular edema), which leads to visual loss. Poor blood flow can also lead to development of abnormal new vessels (neovascularization) not only in the retina, but also in the front part of the eye (rubeosis iridis). These new vessels can cause bleeding in the eye (vitreous hemorrhage) and/or increased eye pressure (neovascular glaucoma). In rare instances, scar tissue can form on the surface of the macula, causing macular pucker formation. Another rare complication is retinal detachment. 

Who is at risk of developing branch retinal vein occlusion?

Branch retinal vein occlusion typically occurs after age 50, with peak incidence between ages 50 and 70. Individuals with a history of systemic hypertension, history of stroke or coronary artery disease, history of smoking, and history of glaucoma are at an increased risk for developing this condition. Rarely, blood clotting abnormalities or certain types of uveitis can predispose to the development of branch retinal vein occlusion.

What is the risk to the other eye?

Almost 10% of patients with branch retinal vein occlusion develop a central retinal vein occlusion or branch retinal vein occlusion in the other eye. 

How is branch retinal vein occlusion treated?

Branch retinal vein occlusion is easily diagnosed with an examination. However, in the first 3-6 months following its incidence, significant intraretinal hemorrhages can make it difficult to predict its course and visual outcome. Once the intraretinal hemorrhages clear, a fluorescein angiogram is usually performed to look for areas of abnormal leakage or poor blood flow within the macula. If poor blood flow is diagnosed, the chances of visual improvement are limited and there are few treatment options. If there is abnormal leakage, but the blood flow is reasonable, laser treatment can be performed.
If abnormal new vessels (neovascularization) develop, laser treatment will cause regression of these abnormal vessels. For persistent vitreous hemorrhage, retinal detachment or macular pucker formation, surgery might be necessary.
Anti-vascular endothelial growth factor (VEGF) injections in the eye are also being investigated for the treatment of macular edema and neovascularization due to retinal vein occlusions.

Central Retinal Vein Occlusion

A primer

The retinal artery supplies blood to the retina. Blood flows through the small arterioles and capillaries and finally leaves the retina through the central retinal vein. Central Retinal Vein Occlusion is a blockage in the central retinal vein that causes backpressure and leads to bleeding, leakage and/or decreased blood flow in the retina.

How does central retinal vein occlusion affect vision?

Central retinal vein occlusion can affect the vision in a number of ways. Poor blood flow (ischemia) through the center of the retina (macula) can severely limit vision. Additionally, exudation and bleeding from the capillaries can cause swelling in the macula (called macular edema), which leads to visual loss. Poor blood flow can also lead to development of abnormal new vessels (neovascularization) not only in the retina, but also in the front part of the eye (rubeosis iridis). These new vessels can cause bleeding in the eye (vitreous hemorrhage) and/or increased eye pressure (neovascular glaucoma). In rare instances, scar tissue can form on the surface of the macula, causing macular pucker formation. Another rare complication is retinal detachment.

Are there different types of central vein occlusion?

Yes, there are two types, ischemic central vein occlusion and non-ischemic central vein occlusion. Non-ischemic generally has good blood flow and a favorable visual prognosis. However, one-third of patients with the non-ischemic condition develop ischemic central retinal vein occlusion over time. That's why careful follow-up is recommended for early detection.|

Who is at risk of developing central retinal vein occlusion?

Central retinal vein occlusion most commonly occurs after age 50. Systemic hypertension, diabetes mellitus and open angle glaucoma are important risk factors. Blood clotting abnormalities are especially important in patients younger than age 50. Rarely, uveitis and certain infections may lead to central retinal vein occlusion.

What is the risk to the other eye?
Almost 10% of patients with central retinal vein occlusion develop a central retinal vein occlusion or branch retinal vein occlusion in the other eye.

How is central retinal vein occlusion treated?
Central retinal vein occlusion is easily diagnosed with an examination. However, in the first 3-6 months following central vein occlusion, significant intraretinal hemorrhages can make it difficult to predict the course and visual outcome. In general, the better the vision is at the time of diagnosis, the better the prognosis. Once intraretinal hemorrhages clear, a fluorescein angiogram is usually performed and can determine whether the central retinal vein occlusion is ischemic or non-ischemic. Laser treatment is not effective for macular edema from central retinal vein occlusion. If abnormal new vessels (neovascularization) develop, laser treatment is usually performed. For persistent vitreous hemorrhage, retinal detachment or macular pucker formation, surgery may be necessary. 

Medical treatment may be needed in patients with blood clotting abnormalities.

Anti-vascular endothelial growth factor (VEGF) injections in the eye are currently being investigated for the treatment of macular edema and neovascularization due to retinal vein occlusions.