There's More To Eye Disease Than Retinopathy
Diabetes linked to several vision complications
Diabetes is associated with a number of eye diseases and conditions that can be annoying, affect your vision, and/or even cause blindness. Most of us with diabetes have heard that diabetic retinopathy (DRT) is the leading cause of blindness for Americans age 20-74. What may surprise some people is the fact that DRT is only one of several different eye problems caused by diabetes, that the most serious of these conditions usually cause few or no symptoms until significant damage has already occurred, and that many of these conditions are linked to complications in other parts of the body, including the kidneys, nerves, and heart. For a moment, I'd like to consider some of the more common eye complications of diabetes.
Diabetic retinopathy, a common and serious eye complication, occurs when high blood sugar damages the tiny blood vessels of the retina, the thin, light-sensitive membrane lining the inside wall of our eyes. Damaged blood vessels leak blood, serum, proteins and fats from the bloodstream that can cause the retina to swell, leading to vision loss (diabetic macular edema). These same damaged vessels can also release chemical signals that cause the growth of new but abnormal blood vessels that bleed profusely, causing formation of fibrous scar tissue that can detach the retina, resulting in blindness (proliferative diabetic retinopathy.) Data from the early 1990s showed that after 10 years, 60% of people with diabetes will have at least the beginning stages of DRT; after 20 years that number jumps to 90%. The keys to preventing vision loss from DRT are tight blood sugar control, tight blood pressure control, and regular dilated eye exams by a knowledgeable eye doctor. Laser treatment of severe DRT can lower the risk of severe vision loss by up to 75%, and a number of new medicines are being developed to treat or prevent this very serious eye disease.
Cataracts are a clouding of the eye's internal lens resulting in reduced vision. All humans develop cataracts with advancing age, but people with diabetes tend to get them at an earlier age, and they tend to develop faster with high blood sugar levels. At first, cataracts may cause a person's eyeglass prescription to change, but their progression often requires surgical removal of the lens to achieve clear vision. Cataract surgery is generally very safe and effective, but people with diabetes have a higher risk of surgical complications (for example, cataract surgery can make diabetic retinopathy get worse). It is important to know that poor blood glucose control can cause temporary swelling of the lens which, in turn, can cause dramatic eyeglass prescription changes over a matter of days or even hours (patients with poorly controlled diabetes are notorious for this phenomenon, which often precedes the development of cataracts.) Tight blood sugar control, wearing ultraviolet blocking eye wear, and avoiding cigarette smoke are the best strategies for avoiding cataracts.
Glaucoma is an eye disease, associated with increased internal eye pressure, which causes damage to the optic nerve and permanent vision loss. It is the second leading cause of blindness in the U.S., and people with diabetes are about 50% more likely to develop glaucoma. Like retinopathy, glaucoma typically causes no symptoms until significant damage to the eyes has already occurred. Glaucoma usually can be treated with eye drop medications, laser procedures, surgery, or a combination of these. The best ways to avoid serious vision loss from glaucoma are regular eye examinations, early diagnosis and adequate treatment.
Diabetic keratopathy occurs when high blood sugar levels damage the eye's clear windshield, the cornea (the transparent tissue covering the colored part of the eye, the iris). The cornea has lots of free nerve endings, and damage to the cornea usually results in significant symptoms (watery eyes, scratchy sensation, redness and pain); unfortunately, some people with diabetes have reduced sensation of their corneas due to neuropathy, which significantly raises the risk of eye infection, scar tissue formation and vision loss. Vigorous eye rubbing should be avoided by all patients with diabetes, and use of contact lenses and laser refractive surgery should be approached cautiously (please see last month's discussion, "Is Laser Eye Surgery Safe?"). Keratopathy can be treated with lubricant eye drops, bandage contact lenses, and eye drop medications, and tight blood sugar control may help reduce symptoms.
For more information on diabetic eye disease, consult Dr. Chous' book Diabetic Eye Disease: Lessons From a Diabetic Eye Doctor, Fairwood Press, Seattle, 2003.
Read more about Dr. Chous here.
Visit Dr. Chous' website here.
NOTE: The information is not intended to be a replacement or substitute for consultation with a qualified medical professional or for professional medical advice related to diabetes or another medical condition. Please contact your physician or medical professional with any questions and concerns about your medical condition.
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