Diabetes and Your Eyes

What is the connection between diabetes and the eyes?
What is diabetic retinopathy and how is it treated?
What other eye problems may be caused by diabetes?

What is the connection between diabetes and the eyes?

Diabetes can damage almost every part of the eye. Indeed, it is the leading cause of adult blindness in the United States. The danger increases with the length of the illness. Two-thirds of diabetics will show signs of eye damage after 15 years, and up to 90 percent will have some eye damage after 30 or 40 years. For this reason, it is important for any person with diabetes to have an annual dilated-eye examination, in which eyedrops are used to dilate the pupil (See Anatomy of the Eye) while the examiner looks at the eye, so that damage can be detected early. A doctor may recommend eye examinations as frequently as every two or three months for some patients, although examinations every six months or once a year will be sufficient in most cases. Anyone with diabetes should be alert for the symptoms of eye problems, such as blurred vision, hemorrhages, or any other unusual change.

What is diabetic retinopathy and how is it treated?

Perhaps the most serious eye problem caused by diabetes is diabetic retinopathy, damage to the light-sensitive retinal cells that line the back of the eye. Some degree of retinopathy can be detected in more than 70 percent of all diabetics 10 years after the diagnosis is made.

Retinopathy is caused by changes in the mural cells that line the blood vessels and prevent them from leaking. Over the years, diabetes leads to a decrease in the number of mural cells, and the capillaries that nourish the retina begin to leak. Sometimes they bulge out, forming aneurysms. The blood that leaks from the capillaries into the vitreous humor, the fluid of the eyes, can reduce the sharpness of vision. Eventually, some of the weakened blood vessels die, and part of the retina can die with them, forming minute clumps of dead tissue called cotton wood exudates.

Diabetic retinopathy can be treated by use of powerful laser light aimed at blood vessels that are weakened or overgrown. This kind of laser surgery may also be performed to thin out retinal tissue, so that the blood supply to the retina is increased. If blood has leaked into the vitreous humor, vitrectomy may be performed to remove the vitreous humor and replace it with an artificial substance.

What other eye problems may be caused by diabetes?

Diabetics are at increased risk of retinal detachment. The retina can become torn or develop a hole, and in advanced cases it can become completely detached from the back of the eye. To detect the early signs of such retinal damage, an examiner will use a contact lens or a lens held very near the eye, so that the edges of the retina are visible.

A retinal tear or hole can be treated by argon laser therapy or freezing. If the retina is completely detached, a gas bubble may be placed in the eye for several weeks to push it back into place. Often, however, surgery under general anesthesia is needed to repair retinal detachment.

Surgery must be done quickly once the problem is diagnosed, because if the retina is not reattached, it loses its supply of nutrients, and the rod and cone cells that are essential for vision will die. One surgical procedure is to use a very cold instrument, a cryoprobe, to make the retina adhere to the back of the eyeball. Another is to push the back of the eyeball toward the retina, using special instruments. This kind of surgery requires a hospital stay of about seven days, with a success rate of 90 percent or better.

Diabetes can also affect the lens, leading to cataract formation. Diabetic cataracts tend to form earlier than most cataracts, and they develop more rapidly. Diabetic cataracts are treated in the same ways as other cataracts, by surgery to remove the damaged lens and replacement with an artificial lens. Cataract surgery generally is done under local anesthesia and without a hospital stay, so that the patient who walks in with clouded vision in the morning can walk out by mid-afternoon with a new, clear lens.