Loss of vision feared most among patients with diabetesby Kenneth Sharpe, M.D.Ophthalmology Many patients who discover that they have diabetes mellitus fear losing their vision more than any other complication of the disease. Patients with diabetes can suffer vision loss from several types of eye disorders such as cataracts and glaucoma. However diabetic retinopathy is the most common cause of vision loss from the disease Diabetic retinopathy is a complication of diabetes in which the disease causes damage to the blood vessels of the retina (a thin film of nerve tissue responsible for the eye’s ability to perceive light which lines the inside of the back of the eye). If this damage advances to the point that swelling and hemorrhaging of the retina occur, some degree of vision loss will result. Currently, approximately one in every 12 people with diabetes age 40 and older has diabetic retinopathy serious enough to threaten his or her vision. Patients with diabetes may not be aware that they have diabetic retinopathy. The disease can and often does progress without causing any symptoms. Therefore it is recommended that patients with diabetes have an eye examination in which the retina is evaluated after drops have been instilled to enlarge the pupil at least once a year. This is important because anyone who has diabetes, whether or not they require insulin, or whether or not their blood sugars are under good control, is at risk for the development of diabetic retinopathy. The longer someone has diabetes the more likely they are to get this disorder. It is estimated that between 40 to 50 percent of those diagnosed with diabetes have some degree of diabetic retinopathy. Although all patients with diabetes are at risk for this complication, clinical studies have demonstrated that patients with better control of their blood sugar levels, blood pressure, and cholesterol have less chance of developing diabetic retinopathy. As with most diseases affecting the blood vessels, smoking greatly increases the risk of this complication. When it does occur, patients who have maintained better control have less severe retinopathy, and therefore may require less extensive treatment. When diabetic retinopathy progresses to an extent that vision is threatened, treatment is recommended. The most generally effective and frequently used treatment modality for diabetic retinopathy is laser surgery. It has been shown that laser surgery in conjunction with the appropriate follow-up care can reduce the risk of blindness by about 90 percent. In situations where damaged blood vessels leak or hemorrhage near the central focus area of the retina, patients may note blurred vision as though looking through a ‘film.’ This condition called diabetic macular edema requires laser surgery to minimize its impact. This surgery often limits further vision loss and many patients experience an improvement. Laser surgery is particularly important in the type of diabetic retinopathy known as proliferative diabetic retinopathy. In this condition, abnormal blood vessels grow along the surface of the retina and into the area of the eye known as the vitreous cavity—the area inside of the eyeball behind the lens of the eye. Laser surgery can often cause these abnormal blood vessels to shrink or, in some cases, completely disappear. If these vessels are not treated effectively, they frequently will lead to hemorrhaging inside the vitreous cavity. Hemorrhages in this area of the eye are noted as dark spots or ‘floaters’ of various sizes and numbers by patients. If the hemorrhaging in this area is extensive, patients experience a severe loss of vision. Fortunately, many of these situations can be corrected, or at least significantly improved, by surgically removing the hemorrhage from the vitreous cavity, a procedure called a vitrectomy. Occasionally, patients who have not received adequate laser treatment (and in some who have) develop extensive blood vessels and scar tissue within the vitreous cavity. If this situation advances unchecked, a retinal detachment will occur. This may cause permanent profound vision loss. If this serious eye disorder develops, very specialized techniques and surgical tools are required to perform to remove the abnormal blood vessels and scar tissue. Although some vision loss is likely, useful vision can often be restored. The use of medications in the vitreous cavity or on the wall of the eye is on the forefront of treatment of swelling of the retina in diabetic retinopathy. This modality is usually considered if laser treatment does not eliminate the swelling. Currently the most commonly injected medication is a prednisone-like drug. This procedure is performed in the office with minimal discomfort and side effects. Implant devices which allow slow release of a medication into the vitreous cavity or other eye tissue will likely become available for use soon. However, a surgical procedure is required to place them in the appropriate location in the eye. Diabetic retinopathy cannot be prevented, but its effects can be lessened in most patients by maintaining good control of blood sugars, cholesterol, and blood pressure; stopping tobacco use; and having regular eye examinations. Treatment, if needed, is more effective if given early. Sharpe can be reached at MUSC Storm Eye Institute, 167 Ashley Avenue,
Charleston, SC 29425, 792-8100, or visit http://www.muschealth.com/eyes.
Friday, Nov. 19, 2004
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