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The Centers for Disease Control and Prevention estimates that approximately 21 million people in the United States have type 1 or type 2 diabetes mellitus (both diagnosed and undiagnosed).1 Therefore, a large portion of the patients whom a pharmacist may encounter will have diabetes. It is important for pharmacists to note that tight glycemic control slows the progression of chronic complications. This outcome was shown in the United Kingdom Prospective Diabetes Study and the Diabetes Control and Complications Trial.2,3
Long-term complications of diabetes include macrovascular complications (involving the large blood vessels), which may lead to heart attack, stroke, and peripheral vascular disease,4 and microvascular complications (involving the small blood vessels), which can lead to diabetic neuropathy, nephropathy, and retinopathy.4
What Is Diabetic Retinopathy?
Diabetic retinopathy (DR), the most common cause of adult blindness in the United States, occurs in 4 of every 10 people with diabetes and causes 12,000 to 24,000 new cases of blindness each year.1,5,6 DR involves damage to the retina (Figure) due to hyperglycemia.7-10 Although there are many proposed mechanisms leading to retinal microvascular damage, the common link between all of them involves the buildup of glucose (hyperglycemia).
Hyperglycemia damages the walls of the microvascular system in the retina, causing the retina to leak fluid (microaneurysm). These microaneurysms block blood and oxygen from reaching the retina. To compensate, the retina signals growth hormone to make new blood vessels (neovascularization). Unfortunately, these new vessels are thin and brittle and may break easily. If the new blood vessels break, blood leaks into the retina, causing more vision loss (intraretinal/vitreous/ preretinal hemorrhages). To stop the bleeding, the body forms scar tissue (retinal scarring). Scar tissue can contract and cause a retinal detachment (separation of the retina's sensory and pigment layers). As a result, severe vision loss or permanent blindness may occur.
What Are the Symptoms?
The longer the duration of diabetes, the higher the risk of developing DR.6 Patients with DR often have no warning signs of vision loss. Early symptoms of DR may include7,10:
What Is the Progression?
DR has 2 stages: (1) nonproliferative and (2) proliferative. In the nonproliferative stage, DR is classified according to severity as mild, moderate, or severe (Table 110). As DR progresses, the amount of swelling of the retina and the damage to the eye increases. In nonproliferative DR, no evidence of retinal neovascularization is apparent.
In proliferative DR, extensive retinal neovascularization is visible. Both stages can cause vision loss.
How Can DR Be Prevented?
The National Diabetes Education Program (NDEP) recommends treatment goals for the ABCs (A1C, Blood Pressure, and Cholesterol) of diabetes.9 Studies have shown that achievement of ABC goals lowers the chances of developing DR2-6 (Table 2). Early detection and treatment can reduce severe vision loss by up to 60%.1 Screening for DR should occur at least every year for patients with diabetes.
How Can DR Be Treated?
The best treatment for DR is prevention. Some patients who are not achieving their ABC goals may develop DR. DR can be treated by4-7,10,11:
What Is the Pharmacist's Role in Preventing DR?
The pharmacist can recommend sight-saving tips?such as achieving and maintaining acceptable glucose, blood pressure, and cholesterol levels?by encouraging medication adherence. The pharmacist also can help with patient education and counseling on the importance of regular diet and exercise and keeping regular eye appointments. In addition, the pharmacist can communicate with other health care providers to ensure the achievement of ABC goals.
Dr. Throm is an assistant professor of pharmacy practice at Midwestern University College of Pharmacy-Glendale, Glendale, Arizona.
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