June 13, 2006 12:00 am
Separation of the retina from the layer of cells behind it. The retina is a light-sensitive layer of tissue lining the inside of the eye; it sends visual signals to the brain. Detachment of the retina may cause permanent blindness and should be regarded as a medical emergency.
So-called tractional retinal detachment can occur in advanced stages of the common complication of diabetes known as diabetic retinopathy. (A detached retina may also result from a tear in the retina or from injury or inflammation of the eye.) In diabetic retinopathy, uncontrolled blood glucose levels damage the small blood vessels called capillaries within the retina, causing changes in blood flow and weakening blood vessel walls. The weakened walls can allow blood or fluid to leak into the retina.
Diabetic retinopathy begins as a relatively mild condition known as nonproliferative, or background, retinopathy, in which the retina receives less blood and nourishment. If not treated, the eye may compensate for this lack of blood supply by growing abnormal new blood vessels on the retina. This growth of new blood vessels, called neovascularization, is the hallmark of the advanced stage known as proliferative retinopathy. These abnormal new blood vessels — which may also grow into the vitreous, the jellylike substance that fills the inside of the eye — tend to bleed and leak fluid into the vitreous. Blood leaking into the vitreous can give rise to “floaters” and in severe cases may blur or block vision. Floaters, which can range in size from small specks to large dark spots, are a common occurrence even in people without retinopathy. But if they appear suddenly, or become more numerous, or if you see light flashes, you should have your eyes checked by a doctor.
If the new blood vessels that form in retinopathy are left untreated, scar tissue can develop along them. As the scar tissue contracts, it can cause tractional detachment, pulling the retina away from the layer of cells (called the retinal pigment epithelium) that lines the back of the eye. The areas of retinal detachment may show up as blank spaces in the field of vision.
In many cases a surgical procedure called a vitrectomy can help improve vision. This involves removing the vitreous, which may be full of blood or may be pulling on the retina. The surgeon makes tiny incisions in the sclera (the white of the eye) and then places a small instrument in the eye to extract the vitreous, which is replaced with a clear fluid. Removing the vitreous also allows the surgeon to pass the required instruments safely to the retinal surface. The surgeon may vacuum blood and remove scar tissue from the surface as well as seal off the blood vessels. Removing the scar tissue from the retina allows it to gradually settle back into its normal position. In some cases, when there are tears or holes in the retina, a gas bubble is used to hold the tear against the back wall of the eye, and laser “photocoagulation” treatment is then used to seal any holes and the edges of any tears.
People with diabetes can lower their risk of retinal detachment by taking steps to ward off retinopathy, getting regular eye examinations, and seeking proper treatment. Tight blood glucose control and tight control of elevated blood pressure have both been shown to significantly reduce the risk of developing diabetic retinopathy. Laser photocoagulation treatment at the nonproliferative stage of diabetic retinopathy can cut the risk of vision loss and the need for vitrectomy by as much as one-half. Thus, the earlier diabetic retinopathy is detected, the better. For adults and for children at least 10 years old, the American Diabetes Association (ADA) recommends getting a comprehensive eye examination by an ophthalmologist or optometrist within five years of the onset of Type 1 diabetes. For people diagnosed with Type 2 diabetes, an eye exam should be performed shortly after the diagnosis is made. The ADA recommends subsequent eye examinations every year in both Type 1 and Type 2 diabetes.
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