Diabetic Retinopathy: The Silent Thief of Sight

AADE Program Session
Thursday, August 12, 2004
4:30 PM - 5:30 PM

Diabetic retinopathy is the leading cause of blindness in the 20- to 60-year-old age group. The disease accounts for approximately 12% of all new cases of blindness in any one year. Diabetic retinopathy is highly prevalent and under diagnosed. It is estimated that 26% of patients with type 1 diabetes and 30% of patients with type 2 diabetes are diagnosed but not receiving timely eye exams. About 55% of diabetic retinopathy patients are believed not to be getting appropriate treatment.

It is important to adhere to a consistent eye exam schedule when treating patients with diabetes. The schedule will depend on the individual case. For type 1 patients, an eye exam should be initiated within 5 years of onset of disease. For type 2 patients, patients should have their eyes examined at diagnosis, since it is likely they have had the disease for several years before diagnosis. Pregnant women with diabetes should be seen in their first trimester. Follow-up exams should be guided by the condition of the fundus, but should occur at least yearly. More advanced changes in the eye indicate the need for more frequent exams. Ophthalmologists will ask the following questions:

• Does the patient have type 1 or type 2 diabetes? (Older patients with type 1 will likely have more changes to the eye; younger patients with type 2 would not be expected to have so many changes)
• How long has the patient had the disease?
• What is the level of blood glucose control?
• What is the level of A1C control? (If A1C levels are near normal, fewer changes in the eye would be expected)
• Has the patient been consistently self monitoring?
• What type of medications is the patient taking, and in what dosages?
• Has there been vision fluctuation? (If so, this indicates that blood glucose levels may have been peaking, the symptoms of which include temporary nearsightedness)
• Who has been this patient's dietician?
• Are there cardiovascular conditions, conditions of the feet or kidney, or neurological problems?

The cause of diabetic retinopathy is not known, but theories include biochemical initiators (buildup of sorbitol and protein kinase), hemodynamic issues (abnormal platelets), and endocrine causes (the growth hormone VEGF causes new abnormal blood vessels to grow). The true cause is probably at least a combination of all 3 factors. Diabetic retinopathy is influenced by factors such as hormones (such as those experienced at puberty), hypertension, and lipids. The disease causes a loss of pericytes, which weakens the capillary walls, causing microaneurysms and capillary nonperfusion (ischemia).

Visual diagnosis can detect disease only at a certain level. Fluorescein angiography helps physicians detect small hemorrhages and capillary abnormalities, as well as other conditions. Newer technologies include optical coherence tomography, in which a laser p produces a 2-dimensional cross-section picture of the retina, and retinal thickness analyzer, in which a laser produces a 3D topographical map of the macula.

The disease is classified into nonproliferative (NPDR) and proliferative (PDR). NPDR is categorized as mild, moderate, severe, and very severe. In PDR, neovascularizations put the eye at risk for hemorrhage and blindness. Treatable changes in the eye as a result of diabetic retinopathy include clinically significant macular edema, vitreous hemorrhage, and tractional retinal detachment. Current treatment options are limited to laser treatment, surgery, and blood glucose control.