Diabetes is a disease where the body has the inability to regulate and utilize sugars in your bloodstream. This lack of insulin results in abnormally elevated sugars in your bloodstream that binds to proteins in the body that impair their ability to function, a process called glycosylation. Eventually, over time, these changes affect the lining of blood vessels and causes blood vessel damage leading to vascular diseases such as heart disease, strokes, and diabetic retinopathy. These same changes are also what results in diabetic kidney disease and numbness in the hands and feet. Diabetes affects the retina in two significant ways. It causes neovascularization (abnormal blood vessels growth) and macular edema (leakage of fluid from abnormal blood vessels).
Neovascularization is the result of very poor blood flow to the retina from narrowed and damaged blood vessels. When this occurs, it is called proliferative diabetic retinopathy (PDR). The unhealthy retina tissues require increased oxygenation and respond by trying to grow new blood vessels to improve blood flow. These new blood vessels can bleed in the eye or form scar tissue that pull and detach the retina, causing significant loss of vision; it is these changes that make diabetes the leading cause of blindness in the United States.
Macular edema, which is swelling from fluid leakage in the center vision of the retina, is also due to abnormal blood vessel remodeling. Instead of growing new vessels that can bleed and cause a retinal detachment in proliferative diabetic retinopathy, the vessels are remodeling and trying to form new connections that are abnormal and leak fluid in the central vision, causing distortion and blurred vision.
Treatment for diabetic retinopathy is aimed at stopping the underlying causes of vision loss. Strong clinical evidence has shown that good blood pressure and sugar control are important at mitigating these changes in the retina. For proliferative diabetic retinopathy, laser treatment to destroy the unhealthy retinal tissue is necessary to stop the ischemic process that is causing abnormal vessels to grow and bleed. Sometimes, PDR is advanced with scar tissue pulling on the retina causing a tractional retinal detachment. In these instances, surgery is necessary to remove the scar tissue and re-attach the retina. Surgery is also indicated sometimes to remove the blood in the eye to restore sight once these abnormal vessels have bled inside the eye. For macular edema, the goal is to inhibit or stop the leaking abnormal microvasculature to reduce retinal swelling. This can be done by a combination of therapies such as laser, topical medicines, or injection of medicine inside the eye that decrease vascular leakage. It is not uncommon to need several treatments to stabilize the vision.
Those with diabetes are highly encouraged to have a yearly exam from both a retina specialist and an optometrist to monitor and maintain the health of their eyes.