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Proliferative Diabetic Retinopathy
Proliferative diabetic retinopathy (PDR) is a more advanced form of diabetic retinopathy and a major cause of visual loss in diabetic patients. Patients at risk for this complication require frequent eye exams and often immediate treatment once the disorder is recognized.
As retinal blood vessels become damaged and close off in diabetic retinopathy due to the cumulative effects of diabetes, the peripheral portions of the retinal circulation begin to close down causing the retina to become oxygen deficient or ischemic. This process is know as retinal ischemia and is believed to be the first step in the development of proliferative diabetic retinopathy. Presumably, the ischemic (nutrient–starved) retina releases a chemical message or growth factor which leads to the growth of new abnormal blood vessels (neovascularization) in the eye. These abnormal vessels often grow on the surface of the retina, at the optic nerve, or in the front of the eye on the iris.
Color retinal photograph centered on the optic nerve (left eye). This picture demonstrates proliferative diabetic retinopathy. Abnormal vessels (neovascularization) are growing from the nerve over the retinal surface and into the vitreous jelly (the clear substance which fills the eye).
Drawing of proliferative diabetic retinopathy
Unfortunately, neovascularization is never good for the eye. The new vessels cannot replace the flow of necessary nutrients and, instead, can cause many problems such as vitreous hemorrhage (bleeding into the gel which fills the eye), traction retinal detachment, and uncontrolled glaucoma (high pressure in the eye). These problems occur because new vessels are fragile and are prone to bleed. As they grow within the eye associated scar tissue may exert traction on adjacent structures. This pulling may produce a distortion of the retina and even lead to a retinal detachment. When the vessels grow in the front of the eye on the colored iris (iris neovascularization) they can clog the fluid outflow channels and cause the pressure in the eye to become very high. This is called neovascular or rubeotic glaucoma.
Color retinal photograph centered on the optic nerve (left eye). This picture demonstrates proliferative diabetic retinopathy. Abnormal vessels (neovascularization) are growing from the nerve over the retinal surface and into the vitreous gel. Some of these vessels have bled into the vitreous (vitreous hemorrhage).
Color retinal photograph centered on the optic nerve (left eye). This picture demonstrates proliferative diabetic retinopathy. Abnormal vessels (neovascularization) are growing from the nerve over the retinal surface and into the vitreous gel. Some of these vessels have bled into the vitreous (vitreous hemorrhage).
Color retinal photograph demonstrating severe proliferative diabetic retinopathy. Abnormal vessels (neovascularization) are growing from the nerve over the retinal surface producing a tractional retinal detachment. In advanced cases of proliferative diabetic retinopathy such as this, a surgical treatment known as a vitrectomy may be required to flatten the retina.
Oftentimes these abnormal blood vessels will grow and the patient will have no symptoms and normal vision. However, these blood vessels are very fragile and can suddenly break open and bleed. When these blood vessels bleed, blood spills out into the normally clear vitreous gel that fills the central hollow part of the eye. This can result in a rapid and sudden decrease in vision. This type of bleeding is termed a Vitreous Hemorrhage. The change in vision from a vitreous hemorrhage can run the spectrum from a few floaters, to cobwebs, to cloudy vision, or to complete loss of vision.
Like a bruise, a Vitreous Hemorrhage will usually be absorbed by the body over the course of several weeks to months, resulting in some improvement in vision. However, sometimes the blood does not clear on its own and surgery is necessary to remove the blood–filled vitreous gel. This surgery is called a Vitrectomy and will be described in a later section.
If caught in its early stages, proliferative diabetic retinopathy can sometimes be arrested with panretinal photocoagulation or the injection of an off–label medication into the eye.