Diabetes and the Eye
by Paul E. Tornambe, M.D., F.A.C.S. M.D., F.A.C
Diabetes is a disease of small blood vessels. The eye contains many small blood vessels so the eye is frequently involved in diabetes.
The eye is the organ of vision. Like the photographer's camera, light enters the eye through the cornea (like the camera lens) and the picture is taken on a fine membrane (like the film) called the retina. The information is then transferred to the brain by way of the optic nerve. The retina contains millions of nerve fibers which are nourished by very small blood vessels. These blood vessels become involved in diabetes.
Sadly, most diabetics go blind for one reason, they are brought to the attention of the eye specialist too late. The National Eye Institute (NEI) sponsored an extensive study on diabetic retinopathy which was published in 1976. The study proved that with appropriate and timely treatment (laser), the risk of severe visual loss from diabetes could be reduced by 70%. Unfortunately , today, diabetics continue to go blind because they come to the attention of the eye doctor too late.
There are two forms of diabetic retinopathy, a background form and a proliferative form. In juvenile diabetes (Type I) the retinopathy can begin as early as ten years after the diagnosis is made. Therefore, a teenager who has had diabetes for ten years must be evaluated at least yearly by an eye care specialist to check for diabetic retinopathy. In background diabetic retinopathy, the retinal blood vessels leak fluid and sometimes blood. If the leakage develops close to the area of central vision, reading vision will be compromised. The NEI trial has proven that laser treatment can stop the progression of diabetic retinopathy. However, as the diabetic ages, other blood vessels start to leak so several laser treatments may be required over a lifetime. We advise that adult onset diabetics (Type II) have an eye examination as soon as diabetes is diagnosed, for they may have had borderline disease for years and the eyes might already be affected.
Proliferative diabetic retinopathy is a more rapidly progressive form of diabetic retinopathy. As the small blood vessels in the eye fail to carry oxygen to the retinal tissue, the tissue elaborates a substance (called VEGF which stands for Vascular Endothelial Growth Factor). This substance tells the body to make blood vessels so more oxygen can be brought to the retina. Unfortunately, the blood vessels the body makes inside the eye are weak and fragile, and tend to break and bleed easily. Again, laser treatment is effective in directly cauterizing these vessels but also improves oxygenation to the retina, which prevents VEGF production. If laser is not applied, the blood vessels continue to bleed, scar tissue forms and the retina is torn as the scar tissue contracts and the retina separates from the back of the eye (retinal detachment) and dies resulting in blindness.
Vitrectomy is an operation developed in the 1970,s which, using space age technology, can remove the blood and scar tissue and restore the retina to its proper position. Again, if instituted early enough, blindness can be prevented. During vitrectomy surgery, instruments less than 1mm in diameter are inserted into the eye. The blood is vacuumed out of the eye and the scar tissue is removed with microscopic forceps and scissors. Laser can then be applied internally to stop the bleeding. The operation takes several hours but is usually done as an outpatient. It is effective in more than 90% of cases.
Presently, medications are being developed to inject into the eye to prevent scar tissue formation. We will see more pharmacologic, manipulation of disease in the next century. We will also likely define the gene(s) that cause this disease and will either manipulate the gene or produce the substance the gene doesn't make to prevent the complications of diabetes.
For the time being, there are three things you can do to minimize the damage to your eyes caused by diabetes. First, if you have a family history of diabetes or are experiencing symptoms of thirst, frequent urination, and weight loss in spite of eating lots of food, you may have diabetes. Early detection and appropriate treatment will significantly reduce the incidence of diabetic complications. See your primary care doctor immediately. Second, if you have diabetes, make every effort to control it tightly. The National Institutes of Health recently completed a very important study which proved, beyond a doubt, that tight sugar control reduces the incidence of blindness, heart disease and peripheral neuropathy. Seek care immediately. Third, exercise frequently. Some types of diabetes are caused by being overweight, if weight is reduced, the diabetes goes away! Exercise is good for everyone, especially diabetics. Exercise helps get the sugar out of the blood stream and into the cells where it does the most good.
Tight blood sugar control, close medical supervision, and exercise will decrease the complications of diabetic eye disease. Just Do IT!
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