Diabetes affects millions of Americans. If diabetes is well-controlled, patients can live long, active lives with the disease. On the other hand, poorly controlled diabetes can result in permanent damage to many parts of the body including the heart, kidneys, brain, peripheral vascular system, and the eyes resulting in increasing disability and early death. Although some effects of diabetes may be obvious, damage to the eyes often goes unrecognized by many patients until the damage is severe and irreversible. It is critically important that diabetics obtain routine eye examinations, even if they feel their vision is good.
Diabetic retinopathy, or damage to the retina and retinal blood vessels, is the leading cause of blindness in diabetics between the ages of 20 to 74. The two leading causes of vision loss in diabetics are proliferative diabetic retinopathy and macular edema. Diabetic retinopathy is caused by too much sugar in the blood, which damages the tiny vessels that nourish the retina. All diabetics are at risk for developing diabetic eye disease, although the risk is increased with poor control and increased duration of diabetes mellitus.
Diabetic retinopathy is classified into four stages, based on exam findings: Mild, moderate, severe, and proliferative retinopathy. Oftentimes, there are no visual symptoms/complaints of diabetic retinopathy in the early stages, and can only be detected by a thorough eye examination.
In the earliest stage of diabetic retinopathy, tiny changes (microaneurysms) are seen within the retina’s smallest blood vessels (capillaries). Mild diabetic retinopathy has no visual impact and does not require treatment. The disease progresses to moderate diabetic retinopathy, and the retinal capillaries begin to close, thereby decreasing the supply of nutrients and oxygen to the retina. In response, the larger retinal blood vessels begin to dilate and become irregular. When diabetic retinopathy becomes severe, widespread areas of the retina lose blood supply. These blood-starved areas send chemical messages to the body to grow new blood vessels, resulting in proliferative diabetic retinopathy.
Proliferative diabetic retinopathy is the most severe form of diabetic retinopathy. At this point, tiny new blood vessels are growing in the retina. These new blood vessels do not develop properly and can easily bleed, causing vision loss. These vessels may grow or leak into the vitreous, the gel that fills the space between the lens and the retina. The new blood vessels can leak blood and impair or completely block vision. Scar tissue can also form from these new vessels which can pull on the retina causing retinal tears and detachment. At the proliferative stage of diabetic retinopathy, the initial treatment option is laser treatment to shrink the abnormal blood vessels. If damage is too severe, a vitrectomy (surgical removal of blood and vitreous gel) inside the eye may be necessary. Statistics show that those with proliferative retinopathy have a decreased risk for further vision loss if they receive timely treatment with laser and/or surgery.
Another important cause of vision loss in diabetics is macular edema, swelling or thickening of the macula (the central part of the retina responsible for fine central vision). This is seen on examination and, if detected properly, may be treated with focal laser treatment and/or injection of medication into the eye. The goal of treatment is to reduce the swelling and seal off any leaking blood vessels. Timely focal laser treatment has been shown to reduce further vision.
Additional complications of diabetics are the accelerated development of cataracts and glaucoma. Cataracts are a natural aging process of the lens inside of the eye. In diabetes, cataracts can grow more rapidly causing decreased and/or blurred vision. Additionally, new blood vessels can grow into the iris (the colored part of the eye), and block the normal flow of fluid out of the eye which in turn, causes eye pressure to rise, causing damage to the optic nerve (the nerve which carries images from the eye to the brain). This is caused by neovascular glaucoma. The prevalence of neovascular glaucoma is significantly higher in patients with proliferative diabetic retinopathy. This form of glaucoma can be quite difficult to treat and may require laser procedures, intraocular injections, and surgery.
The only way to avoid diabetic eye disease is to actively participate in your healthcare. The keys to success are maintaining optimal blood sugar control, keeping blood pressure at target, controlling cholesterol levels, getting daily exercise, and avoiding smoking. It is important to have yearly eye exams with an eye care provider for early detection of any diabetic changes in the retina. Early detection is the best defense against vision loss from diabetic eye disease.
http://www.nei.nih.gov/health/diabetic/retinopathy.asp
http://diabetes.webmd.com/retinopathy-causes-treatments
http://www.mayoclinic.com/health/diabetic-retinopathy/DS00447
http://www.aao.org/aao/publications/eyenet/200607/pearls.cfm
http://www.diabetes.org/diabetes-basics/diabetes-statistics/?loc=DropDownDB-stats
