Central Retinal Vein Occlusion (CRVO)
Just like any other tissue in your body, the retina has a blood supply. The central retinal artery travels down the optic nerve and supplies blood to the entire retina. At the point the central retinal artery enters the retina, it begins to progressively branch into smaller arteries and then microscopic capillaries, which supply oxygen and nutrients to the retina. This arterial system connects to a parallel set of veins that drain into larger veins leading to the central retinal vein, which exits the retina also through the center of the optic nerve. Some of the most common problems a retina specialist sees are related to abnormalities in the blood vessel system of the retina.
A central retinal vein occlusion is a blockage of the central retinal vein within the optic nerve. Central retinal vein occlusion usually presents with sudden onset of blurred vision. Eye examination shows scattered retinal hemorrhages, dilation and tortuosity of the retinal veins and retinal swelling (edema). Retinal imaging with fluorescein angiography and optical coherence tomography (OCT) are helpful in confirming the diagnosis.
There are two types of central vein occlusions: ischemic and non-ischemic. Non-ischemic vein occlusions have a better prognosis. Ischemic central vein occlusions occur in older individuals and are associated with poor retinal blood supply, have worse vision and less chance of improvement.
Central retinal vein occlusions are associated with other systemic medical conditions such as high blood pressure, high cholesterol, diabetes, heart disease and stroke. Central vein occlusion is also associated with glaucoma (high intraocular pressure). Changes in blood vessels, which occur with aging, are also a factor. Rarely, central vein occlusions can be associated with blood clotting disorders. In some cases, central vein occlusion occurs for no apparent reason. Central vein occlusion has a better prognosis in young people.
Some central vein occlusions may be mild, cause little or no vision loss and may not require treatment. However, more severe cases may lead to impaired retinal blood supply, retinal hemorrhages and retinal swelling (edema) that can cause loss of vision. Unfortunately, there is no way to reverse a blocked vein. Medications, which must be injected into the eye periodically, may improve vision. The injections may be needed as frequently as once a month but later on the treatment interval can be extended and, in some cases, treatment may be stopped.