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Diabetic Retinopathy

The retina is the light-sensitive surface at the back of each eye. This is where the light falls that has been focused by the lens. It is enormously complex, made up of ten distinct cell layers composed of millions of nerve cells. At the ‘top’ of these layers, where the light strikes, are the cells that directly respond to light, the rods and cones. Cone cells see color while rod cells concentrate on black and white and the overall contrast of light within a scene. The retina is to sight what the ear drum is to hearing: the location where the essential first step in each process begins.

Any pathology of the retina can be called a retinopathy. In diabetic retinopathy (DR), tiny blood vessels in the retina begin to fail. This is due in part to the high sugar levels in the blood of diabetics. A major reason for people trying hard to achieve “good control” over their blood sugar levels is to prevent DR. Retinopathy can occur with either type 1 or type 2 diabetes. Almost 50% of all people with diabetes have some degree of diabetic retinopathy.

Basically, the longer one has diabetes and the more poorly blood sugar is controlled, the greater the risk of DR developing and progressing. Untreated DR can seriously impair vision, up to and including causing complete blindness. For reasons not understood, African-Americans and Hispanics with diabetes have a greater chance of developing DR.

Unfortunately, DR can be present for many years without causing any symptoms. Therefore, to protect their vision, all diabetics should have their eyes examined at least once every year. The eye doctor should be told if a patient has diabetes, so they will specifically examine the retina. This is best done by first dilating the pupils, then looking past the lens of the eye with a light, to see the retina and its many fine blood vessels. In healthy eyes, these vessels are tiny and thin.

As DR begins and progresses, the retinal vessels begin to bulge in places, due to blockages to the blood flow. A vessel may also bleed into the eye and the doctor can see signs of this. Due to the initial blockages, the eyes sense they need more oxygen and respond by growing more vessels in the retina, and this overgrowth of vessels can be detected in an exam of the retina.  Since the vessels are becoming more numerous, this last stage of DR is called “proliferative retinopathy.” Unfortunately the many new blood vessels make the situation worse, not better. Often present along with DR is macular edema, a swelling at the center of the retina (the macula) where the highest concentration of vision nerves sit. This can be another cause of vision impairment, with or without DR. These conditions are painless.

Once symptoms are noticeable to a person, chances are the diabetic retinopathy process is well under way. Bleeding inside the eye can appear as spots or floaters in one’s vision. In other cases, vision may sometimes be blurry, or the person experiences double-vision. If any of these signs suddenly appear, see an eye doctor as soon as possible. Sometimes the symptoms will spontaneously disappear for a while, but this is not a true recovery and an eye doctor should still be seen. Of course, there can also be other causes for some of these symptoms, which the eye doctor will determine.

If retinopathy is discovered before the proliferative stage, ‘treatment’ consists of making greater efforts to control one’s blood sugar, blood pressure and cholesterol levels, with medication if necessary. Any sign of proliferative retinopathy will be treated with a laser surgery technique that destroys many of the abnormal vessels. This itself can cause a slight loss of sight, but it keeps the retinopathy from getting any worse.

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