Macular Degeneration 101
The fundamentals of macular degeneration (and how to avoid it)
By A.Paul Chous, MA, OD, FAAO
I examined a wonderful, talented, and smart lady this week who complained of reduced vision in her right eye for the last ten days. Jane has celebrated 72 birthdays and has had type 2 diabetes for 23 years – she has been my patient for 15 of them. She has always had excellent blood glucose and blood pressure control and has, fortunately, never developed any severe diabetic retinopathy. Unfortunately, Jane has continued to smoke a pack of cigarettes every day, even after being urged to quit multiple times by me, her endocrinologist, and her dentist, and even after I diagnosed her with the earliest stages of macular degeneration four years ago. Unfortunately, at this week's visit I discovered a cluster of abnormal, leaking blood vessels beneath the retina of Jane's right eye, exactly in the center of her vision. Unfortunately, it is highly unlikely that Jane will ever see very well out of her right eye again.
Although diabetic retinopathy is the leading cause of new blindness in Americans under the age of 74, it is not the leading cause of severe vision loss for all Americans. This dubious distinction goes to another eye disease that affects more than 9 million people in our country: age-related macular degeneration (ARMD). In fact, macular degeneration accounts for about 50% of legal blindness in the Western World (defined as vision less than 20/200 with the use of prescription lenses) and affects 1 of 3 Americans past the age of 80. Unfortunately, with the aging population these numbers will undoubtedly grow, and as those of us with diabetes live longer our risk of developing ARMD will grow as well.
ARMD occurs when the most visually sensitive part of the eye's retina, the macula, becomes unable to clear away the normal by-products of retinal metabolism, leading to impaired circulation, loss of the cells that send information from the retina to the brain, abnormal blind spots in the center of vision and permanent, uncorrectable loss of visual clarity (see figure below). The root cause of ARMD is thought to be "free radical" damage to the retina as a result of biochemicals that our bodies produce in response to inflammation, or from toxic chemicals absorbed via inhalation of smoke. This is why ARMD may be associated with both obesity and cardiovascular disease, and also why it is highly associated with cigarette smoking (three times the risk). A family history of ARMD also substantially increases our risk, as do white race, fair complexion with light eye color, and female gender.
Two general types of ARMD are recognized: "wet" and "dry." The first refers to the development of abnormal blood vessels beneath the surface of the retina which leak fluid and blood, whereas the second lacks this feature. Both types can lead to mild, moderate or severe vision loss, but "wet ARMD" develops much more quickly (in a matter of days or weeks) and tends to lead to more severe visual impairment, whereas "dry ARMD" progresses more slowly (over months or years). The majority of patients develop dry ARMD, but a significant minority of these patients develop the "wet" form of the disease over time, as with Jane.
An example of how my face might appear to someone with macular degeneration (Please don't tell me it's an improvement, even if that might be true!)
Treatment of "wet" ARMD includes laser treatment of abnormal vessels, surgery and, most recently, injection of medicines called vascular endothelial growth factor inhibitors (VEGFIs) that block the formation of new blood vessels (these same drugs are now also being used to treat proliferative diabetic retinopathy). Unfortunately, even with state-of-the-art treatment, visual results are often not good with "wet ARMD."
There are no medical treatments for "dry" ARMD, though supplementation with lutein/zeaxanthin (protective pigments found in the macula and contained in dark, green leafy vegetables) and certain antioxidants have been shown to lower the risk of progression for particular stages of "dry" ARMD (consult your eye doctor for the specifics). The single most important thing anyone with or without diabetes can do to prevent vision loss from ARMD is to avoid or quit smoking. Beyond that, eating an "anti-inflammatory" diet rich in colorful fruits and vegetables, high in omega-3 fatty acids (think sardines, salmon and herring – or a fish oil supplement), with a minimum of saturated fat, wearing ultraviolet blocking lenses, and getting regular dilated eye examinations is your best defense against this terrible, all-too-common eye condition.
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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