Diabetic Retinopathy

What Is Diabetic Retinopathy?

Diabetic retinopathy, a major cause of vision impairment and blindness, is a disorder in which small blood vessels nourishing the retina (back layer of the eye) weaken and break down or become blocked. The retina is essential to vision and is somewhat like the film of a camera – receiving an image to be “developed” in the brain. Its delicate network of light-sensitive nerves is normally supplied with oxygen and other nutrients by blood vessels that, in diabetic retinopathy, may begin to do one of the following:

• bulge out (aneurysm)
• leak fluid
• bleed
• grow abnormally
• close down completely

Who Is At Risk?

Diabetic retinopathy is one of the complications associated with the general circulatory problems developed by people who have diabetes. The longer a person has diabetes, the greater the risk of retinopathy-more than 40 percent of those who have diabetes for 15 or more years have some degree of blood vessel damage. Of these, a smaller percentage develops the most serious consequence of the disease-severe vision impairment or blindness.

The disease does not follow a predictable course; it does not just afflict people who have had diabetes for many years. It can appear within the first year or two after the onset of the disease. For some people, retinopathy is one of the first signs that they have diabetes.

Early treatment of retinopathy often improves the potential for saving sight. Every diabetic should receive regular care from a doctor and should also see an eye care specialist before any visual symptoms appear. An ophthalmic exam by a specialist should be repeated at least once a year for both adult and child diabetics. Pregnancy, high blood pressure and smoking can worsen this eye condition.

What Are The Stages Of The Disease?

In the early stages of diabetic retinopathy, blood vessels swell and sometimes bulge (diagram #1). The vessels may leak fluid, which can accumulate in the retina and distort vision. Although these fluid deposits may clear up on their own, they often leave fatty deposits which can also interfere with vision. Later, vessels may begin to bleed within the retina.

In many cases when the small blood vessels close down, new abnormal blood vessels may develop. These abnormal blood vessels are not able to provide nourishment to the retina. They can, however, penetrate the vitreous, the clear jelly-like fluid filling the major portion of the eye’s interior (diagram #2).

The new vessels, which are very weak, can bleed into the vitreous, causing dark spots, cobweb-like strands or severe clouding in the field of vision. Sometimes, the formation of fibrous scar tissue can pull the retina away from its source of nutrition on the back of the eye (diagram #3). If the retina becomes detached or tears, the result can be serious loss of vision or even blindness.

Cross-section showing blood vessels in retina lining the back of the eye. In diabetes, they often bulge (aneurysm) and leak

Weak, new vessels grow,later rupture and spread blood into the eye's interior (vitreous) resulting in cloudy vision.

Scars form, shrinking the vitreous and pulling on the retina-tearing or detaching it. Result: vision loss or blindness.

What Treatment Is Available?

The treatment for some forms of vision-threatening retinopathy is photocoagulation: the use of an intense beam of laser light to seal leaking or bleeding vessels. In this procedure, a laser beam is carefully targeted to problem areas that have been pinpointed earlier with the aid of a fluorescent dye. In advanced cases of retinopathy, photocoagulation is more extensive and can be used to repair torn retinas.

Laser therapy can also control or prevent the abnormal growth of new, non-functional blood vessels. This form of treatment is not, however, appropriate for every case of diabetic retinopathy.

Another recent treatment for advanced cases of diabetic retinopathy, in which abnormal vessel growth is severe and bleeding persists, is called vitrectomy. In this technique, a delicate instrument is used to remove the blood deposits and tear tissue strands within the vitreous fluid by suction. At the same time, through another channel of the instrument, a clear salt solution is injected to replace the vitreous.

Hope For The Future

Medical scientists continue to work toward a better understanding and improved management of diabetic retinopathy. In the meantime, early diagnosis of retinopathy and close observation by an eye care specialist are major objectives in the successful treatment of patients with diabetes. It is important for the diabetic patient to be aware that dangerous changes in the retina often occur before vision is affected