Diabetic Retinopathy: Eye Care

Content provided by the Faculty of the Harvard Medical School

Diabetic retinopathy

With cases of diabetes rising precipitously, the eye problem known as diabetic retinopathy — which can cause vision loss and blindness — is becoming a serious public health issue.

The most common forms of diabetes are designated as type 1 and type 2. In type 1 diabetes, an autoimmune disease, the pancreas is unable to produce insulin, which cells need in order to use blood sugar (glucose). A combination of abnormalities is responsible for type 2 diabetes, but the disorder usually develops when people become overweight and develop insulin resistance, so that they are unable to metabolize blood sugar. While the mechanisms that cause type 1 and type 2 diabetes differ, both disorders result in high blood sugar levels which, left untreated, have serious long-term consequences on other parts of the body, including the eyes. People with diabetes are at greater risk than the general population for developing cataracts and glaucoma, but a third problem — diabetic retinopathy — is most likely to cause severe vision loss and even blindness.

Diabetic retinopathy occurs when abnormal blood sugar levels damage small blood vessels in the retina. Damage to the retina can lead to vision problems, including permanent vision loss.

Diabetic retinopathy occurs in two stages. In the earlier stage, known as nonproliferative or background retinopathy, the walls of the small blood vessels become abnormal and weaken. They leak fluid into the surrounding tissue, often leaving deposits of protein and fat called hard exudates. The vessels also develop microaneurysms, tiny bulges or balloons in their walls that tend to leak red blood cells into the retina. As the condition progresses, the abnormal vessels begin to close, robbing the retina of its blood supply. Nerve fibers die off because of poor circulation and lack of oxygen, creating white cottony patches known as soft exudates.

These changes may not necessarily alter your vision. But if the fluid or blood leakage occurs near the macula — the part of the retina responsible for sharp, central vision — your sight will be impaired. When fluid leaks into the center of the macula, the macula can swell, blurring vision. This condition is called macular edema.

Severe impairment occurs when retinopathy advances to the proliferative stage. This is when the severely diminished blood flow causes the damaged retina to try to repair itself by sprouting new blood vessels. However, these new vessels grow abnormally and proliferate into the vitreous humor, the gel-filled compartment of the eye in front of the retina. The new vessels are fragile and prone to leak blood and break. When they bleed into the vitreous humor, they can block the passage of light and cause a sudden loss of vision. The blood is usually reabsorbed, but scar tissue often forms. The scar tissue exerts traction on the retina, pulling it away from the back of the eye, which can lead to permanent vision loss (see "Retinal detachment").

As diabetic retinopathy progresses, you may notice spots and floaters in your vision. Central vision may become distorted. Photograph courtesy of the National Eye Institute.

Last updated:	June 19, 2007