VEIN OCCLUSIONS

There are two types of blood vessels found in the eyes. One type of blood vessel known as an artery brings blood into the eye and a second type of blood vessel known as a vein brings blood out of the eye. In the optic nerve are two major blood vessels, the central retinal artery and the central retinal vein. When the artery enters the retina, it breaks up into branch retinal arteries. The blood then goes into a capillary bed and leaves the retina via branch retinal veins which lead into the central retinal vein. Various conditions can cause a blockage of blood in the central retinal vein or in a branch retinal vein.

When a retinal vein becomes occluded, blood can enter the retina but has difficulty leaving. As a result, the retina swells up with blood and fluid and the visual acuity may be decreased. If large segments of the retina are involved, ischemia or a lack of oxygen can develop and new blood vessels may begin to form both in the front of the eye and in the back. These new blood vessels are very harmful to the eye and can result in bleeding, membrane formation, tearing of the retina, elevated pressure in the eye, and damage to the optic nerve.

In order to assess the likelihood of new blood vessel formation we do a test called a fluorescein angiogram. This test involves injecting a dye into the arm while simultaneously taking pictures of the back of the eye. With this test we can determine the likelihood of new blood vessel formation. If this likelihood is great, a panretinal laser treatment may be recommended. Panretinal laser treatment involves destruction of areas of the retina not vital to central vision. By destroying these less essential areas we can greatly reduce the chance of new blood vessel formation and can often cause regression of new blood vessels which have already formed.

With branch retinal vein occlusions it is sometimes possible to partially restore visual loss. This is accomplished by treating the area of the retina affected by the branch vein occlusion.

Various conditions may be responsible for causing vein occlusions. These include high blood pressure, atherosclerotic vascular disease, glaucoma, inflammation of the veins and thickening of the blood. Patients with vein occlusions very often will have a large battery of tests performed in order to rule out inflammatory diseases which can cause a vein to become blocked.

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