By Cherra F. Pumphrey, M.D., HarborSide Internal Medicine –
According to the American Diabetes Association, 25.8 million people in the United States (8.3% of the population) have diabetes mellitus type II. While patients with diabetes mellitus are at increased risk of developing cataracts and glaucoma, the most common diabetic eye disease is diabetic retinopathy.
Diabetic retinopathy is retinal damage caused by diabetes. The retina consists of light-sensitive nerve tissue located in the posterior aspect of the eye where images projected from the lens are converted to electrical impulses that are then sent along the optic nerve to the brain. Diabetic retinopathy encompasses a spectrum of retinal changes, which are divided into four stages. The initial stage, mild nonproliferative retinopathy, involves development of microaneurysms (swelling of minute blood vessels in the retina). The second stage, moderate nonproliferative retinopathy, involves blockage of some of the blood vessels that supply the retina. The third stage, severe nonproliferative retinopathy, is associated with occlusion of a significant number of blood vessels to the extent that several areas of the retina are deprived of an adequate blood supply. When part of the body receives an inadequate blood supply, neovascularization (new blood vessel growth) may result. The fourth stage, proliferative retinopathy, is associated with neovascularization along the retina and vitreous humor (gel within the eye); these new blood vessels have fragile, thin walls and may leak blood, possibly resulting in vision loss.
In addition to vision loss secondary to bleeding from abnormal blood vessels associated with proliferative retinopathy, vision impairment may also occur with macular edema (fluid leakage into the portion of the retina necessary for sharp central vision). While it is more likely to develop in advanced stages, macular edema may emerge at any stage of diabetic retinopathy.
Proliferative diabetic retinopathy and macular edema are often treated with laser surgery performed by a retina specialist. Laser surgery and appropriate follow-up care can reduce the risk of blindness by up to 90%. In addition to laser surgery, other treatment modalities may also potentially be indicated for each of these conditions. When severe bleeding occurs with proliferative retinopathy, a vitrectomy (removal of the vitreous humor) may be necessary. In treating macular edema, intravitreal injections of a vascular endothelial growth factor antagonist (ranibizumab and bevacizumab, for example) may be appropriate.
Vision may not be adversely affected until diabetic retinopathy has reached more advanced stages. Early detection and appropriate treatment of diabetic retinopathy may potentially prevent/delay progression of disease, resulting in better vision for a longer period of time. Therefore, even in the absence of symptoms, patients with diabetes mellitus should have a dilated eye examination by an optometrist or an ophthalmologist at least once per year (more often if so recommended by the eye physician). Furthermore, if patients develop any acute vision changes, they should seek immediate medical attention.
Approximately 45% of patients diagnosed with diabetes mellitus have diabetic retinopathy. According to the National Institute of Health, diabetic retinopathy is the leading cause of blindness in adults in the United States. Diabetic patients are strongly advised to achieve and maintain optimal control of blood glucose levels as good blood glucose control has been shown to delay onset and slow progression of diabetic retinopathy. In addition to appropriately managing diabetes and other medical conditions as well as striving for overall wellness, utilizing proper eye protection when engaging in activities that might result in eye injury and undergoing regular thorough eye examinations by an eye physician increase the likelihood of achieving and maintaining good vision. Diabetic patients are challenged to strive for optimal blood glucose control and to see their eye physician for a comprehensive eye evaluation at least once per year!
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