When it comes to diabetes-related eye complications, the good news is that most cases of severe vision loss due to diabetes are preventable. The bad news is that tens of thousands of people still lose vision to diabetes each year, despite all that is known about prevention and treatment.
Diabetes is the leading cause of new blindness for American adults between the ages of 20 and 74. The American Diabetes Association (ADA) estimates that 12,000–24,000 people in the United States lose their vision to diabetic retinopathy each year, and studies have shown that people with diabetes have a fivefold to twenty-fivefold increased risk of blindness in their lifetimes.
However, these numbers very likely underestimate the true incidence of vision loss and blindness, because diabetes can cause a variety of eye diseases other than retinopathy, several of which can cause severe visual impairment (see “Eye Diseases Associated With Diabetes” ). Moreover, these statistics ignore vision loss less severe than “legal blindness” (defined as vision on the eye chart worse than 20/200 with the use of prescription lenses or severe loss of peripheral vision to within 20 degrees of central vision). But even less severe vision loss can and does substantially affect quality of life for thousands of people with diabetes.
Why do so many people continue to lose their sight to diabetes when so much is known about preventing and treating these complications? This question has dogged eye doctors, diabetes specialists, and public health experts for years, and the consensus answer boils down to four critical and interrelated elements: the epidemic of new diabetes cases, lack of patient education, lack of patient motivation and support, and lack of access to excellent diabetes care.
I do not pretend that these issues are easily solved, but I believe the tools are at hand to greatly reduce all the dreaded complications of diabetes — including blindness — as well as the human suffering they entail. I believe that a collaborative effort among people who have diabetes, health-care providers, and policy makers is the surest and fastest route to that end.
With that goal in mind, here is some of what I have learned in my 36 years of living with diabetes and my 15 years as a doctor of optometry specializing in diabetes care and education. Most of these strategies, in addition to minimizing the risk of eye complications, will go a long way toward preventing all diabetes complications. This is not all that surprising since eye problems caused by diabetes often go hand in hand with nerve, kidney, and cardiovascular disease.
Blood glucose control
Keep your blood glucose levels as close to the normal range as possible. High blood glucose levels are directly or indirectly responsible for all forms of diabetic eye disease. The landmark Diabetes Complications and Control Trial, published in 1993, showed that in people with Type 1 diabetes, each 10% reduction in average blood glucose levels, as reflected by a person’s glycosylated hemoglobin (HbA1c) level, lowers the risk of developing diabetic retinopathy by roughly 60% and lowers the risk of preexisting diabetic retinopathy getting worse by 43%.
This means, for example, that if your HbA1c level is typically 7.0% (equivalent to an average blood glucose level of 172 mg/dl) and you bring your HbA1c down to 6.3% (equivalent to an average blood glucose level of 147 mg/dl), you have dramatically reduced your chances of developing retinopathy. If you already have some degree of retinopathy and you lower your HbA1c level by this amount, you have substantially lowered the chances of your retinopathy getting worse. These risk-reduction statistics hold true until HbA1c levels are below 5.0% (which is equivalent to an average blood glucose level of 101 mg/dl), at which point the risks of retinopathy development and progression are minimal.