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Causes of Nonproliferative and Proliferative Diabetic Retinopathy
Causes of Nonproliferative and Proliferative Diabetic Retinopathy
Diabetic retinopathy is caused by long periods of high blood sugar (glucose) levels damaging the retina's blood vessels. This leads to two progressive stages of disease:
- Nonproliferative diabetic retinopathy (NPDR): During this early disease stage, the damaged blood vessels leak blood and other fluid into the eye. Many diabetic patients have mild cases, with no symptoms. If problems do occur, they often affect the macula, the central part of the retina responsible for more focused vision like during reading. These complications include:
- Macular edema: Leaking fluid swells or thickens the macula, disturbing its operation.
- Macular ischemia: The damaged vessels close, causing vision to blur as the macula’s blood supply is cut off.
- Proliferative diabetic retinopathy (PDR): Uncontrolled disease can turn into proliferative diabetic retinopathy as the retina grows new blood vessels (neovascularization) to replace the ones that closed. The new vessels do not work properly, though, so the retina does not get all the blood it needs. These vessels can cause severe problems in the retina, as well as the rest of the eye. That can cause difficulty with both central focusing and side (peripheral) vision, with complications such as:
- Retinal detachment: Scar tissue from the new blood vessels can cause the retina to wrinkle or detach. (Learn more about retinal detachment.)
- Glaucoma: New blood vessels can block the normal flow of fluid out of the eye, building up pressure and damaging the optic nerve. (Learn more about glaucoma.)
- Hemorrhaging: The new blood vessels can bleed into the gel (vitreous) in the center of the eye.