The chemical changes caused by diabetes can damage blood vessels throughout the body, including the fine blood vessels in the retina, or the seeing part of the eye. This damage is called diabetic retinopathy of which there are two kinds:
Non-Proliferation Diabetic Retinopathy (NPDR) occurs when the retinal blood vessels start to leak, causing blood or fluid to seep into the retina.
The retina becomes thick and swollen and does not work correctly. If the leaking happens in the macula, (the central part of the retina), vision will be blurred. If the leaks occur on the periphery of the retina, there may be no impact on vision.
Proliferative Diabetic Retinopathy (PDR) occurs when the retinal blood vessels close, cutting off nutrition to the retinal tissue. Abnormal new blood vessels, called neovascularization, may form and cause bleeding and scar tissue. The bleeding (called vitreous hemorrhage because the blood fills up the vitreous cavity inside the eye) and scar tissue can result in blindness if not treated. The earlier neovascularization is discovered, the better the chance that surgery can save vision. Both types of diabetic retinopathy may occur without a noticeable change in vision. It is therefore imperative, if you have diabetes, to have your retinas examined every six months by an eye specialist.