The Facts
The retina, at the back of the eye, provides a window to the circulatory system. By examining it, a doctor can inspect a sample of the body's blood vessels and detect early signs of complications of diabetes or high blood pressure, as well as many other diseases.
Some of the kinds of damage that your doctor may see in your retina are hypertensive retinopathy, a complication of high blood pressure (hypertension), and diabetic retinopathy, a complication of long-term diabetes.
It's unusual for hypertension to impair vision, but hypertensive retinopathy can lead to blockage of retinal arteries or veins which, in turn, may eventually result in the loss of vision.
Diabetic retinopathy is a deterioration of the blood vessels in the retina. It usually affects both eyes, and is the leading cause of blindness in North America. Almost all people with diabetes show signs of retinal damage after about 30 years of living with the condition.