Frequently Asked Questions
Risk Factors and Causes
Having diabetes puts you at risk of retinopathy, whether you have type 1 diabetes or type 2 diabetes and your risk increases the longer you have the disease. This is way it's so important to have a comprehensive dilated eye exam at least once a year.
Other risk factors for diabetic retinopathy include:
- Poorly controlled blood sugar levels
- High blood pressure
- High blood cholesterol
- Hispanic or African-American heritage
How does diabetic retinopathy cause vision loss?
Over time, diabetes affects the circulatory system of the retina. When damage to the capillaries in your eyes occurs it's called diabetic retinopathy. Blood vessels damaged from diabetic retinopathy can cause vision loss in two ways:
- Fragile, abnormal blood vessels can develop and leak blood into the center of the eye, blurring vision. This is proliferative retinopathy and is the fourth and most advanced stage of the disease.
- About half of the people with proliferative retinopathy also have macular edema. Fluid can leak into the center of the macula, the part of the eye which is responsible for clear straight-ahead vision. The fluid makes the macula swell, blurring vision. This condition is called macular edema and can occur at any stage of diabetic retinopathy.
Diabetic retinopathy occurs in two types, usually affecting both eyes similarly:
Nonproliferative diabetic retinopathy (NPDR):
This type, also called background diabetic retinopathy, is an early stage of the disease. It's the most common type of retinopathy, and symptoms are often mild or nonexistent.
In NPDR the walls of blood vessels in the retina weaken. Tiny bulges called microaneurysms protrude from the walls of the small vessels in the retina. The microaneurysms may begin to leak, oozing fluid and blood into the retina. As NPDR progresses, other signs of damage appear. These include swelling or beading of some of the larger retinal veins and patches of swollen nerve fibers, which are called cotton-wool spots because clinically they look like fluffy wisps of cotton.
Mild NPDR may not affect your ability to see clearly. Vision problems from more severe NPDR are usually the result of swelling (edema) of the central part of the retina (macula) - a condition called diabetic macular edema (DME) - or the closing of capillaries, which reduces blood flow to the macula (macular ischemia). When the macula can't function properly, your central vision decreases.
Proliferative diabetic retinopathy (PDR):
A more advanced form of the disease when the retinopathy becomes proliferative and abnormal new blood vessels grow (proliferate) in the retina or the optic disc. The new blood vessels (neovascularization) grow because areas of the retina become oxygen-deprived or ischemic and your body is attempting to maintain adequate oxygen levels within the retina. Unfortunately, these delicate vessels hemorrhage easily. They grow along the retina and along the surface of the clear, vitreous gel that fills the inside of the eye. By themselves, these blood vessels do not cause symptoms or vision loss; however, they have thin, fragile walls. If they leak blood, severe vision loss and even blindness can result. In the later phases of the disease, continued abnormal vessel growth and scar tissue may cause serious problems such as retinal detachment and/or a form of glaucoma associated with the growth of abnormal blood vessels on the iris, the colored portion of the eye surrounding the pupil (neovascular glaucoma).
Visual perception photos above of ocular disease come from the NIH website.