Diabetic Retinopathy
Diabetic retinopathy is the leading cause of blindness for adults in the United States. Even with the best control of one's blood sugar, a diabetic can still develop retinopathy. Some patients even have retinopathy at the time that they are first diagnosed with diabetes. Background diabetic retinopathy is an early stage of this condition. This type of retinopathy is manifested by damage of the small blood vessels in the retina, usually around the center of the retina (macula).
Leakage of blood causes hemorrhages in the retina and leakage of fluid causes edema (swelling of the retina). Swelling of the retina can reduce vision and cause metamorphopsia (distortion). This condition often necessitates fluorescein angiography in its diagnosis and laser photocoagulation in its treatment.
The more advanced form of diabetic retinopathy is proliferative retinopathy. Progressive ischemia (oxygen deprivation) of the diabetic retina causes the abnormal growth of blood vessels on the retinal surface (neovascularization). Though the blood vessels themselves often cause no change in vision, they can easily rupture and fill the eye with blood (vitreous hemorrhage). This is a major cause of catastrophic visual loss in a diabetic.
Even worse, these abnormal blood vessels can cause tractional elevation of the retina and produce a retinal detachment. Again, laser photocoagulation is the treatment of choice for proliferative diabetic retinopathy. For vitreous hemorrhage and retinal detachment, however, vitrectomy is often necessary. The most important factor in preventing the development and progression of diabetic retinopathy is good control of the blood glucose. Hypertension, hyperlipidemia, and pregnancy can result in more extensive retinopathy and increase the risk of visual loss.
A new potential treatment for diabetic retinopathy is an oral medication known as protein kinase C inhibitor. The Retina-Vitreous Center is actively enrolling patients in a new multicenter, randomized, placebo-controlled clinical trial of this drug in patients with certain degrees of diabetic retinopathy. A safe and effective oral treatment for diabetic retinopathy would be a major breakthrough in the fight against blindness.
Intraocular steroid injection has become a common for treatment macular edema in diabetic retinopathy, but the steroids have certain risks, such as cataract development and intraocular pressure elevation. The Retina-Vitreous Center is studying the treatment of diabetic macular edema with injections of Macugen, a new drug which was FDA approved recently for the treatment of macular degeneration. Phase II trials have shown that Macugen reduces macular edema, and more extensive Phase III testing is now under way. The drug is delivered by intraocular injection, but does not seem to carry the same risk of glaucoma and cataract associated with intraocular steroid injection.
