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Diabetic Retinopathy

Diabetic retinopathy (reh-tin-AH-puh-thee) is an eye condition that can affect the retina in patients who have had diabetes for many years. It is a major cause of poor vision and blindness. Although not totally preventable, when it is diagnosed early it can be treated early and be less damaging to vision.

What Is Retinopathy?

The term retinopathy means "a disease process that affects the retina." The retina is the light-sensitive membrane that lines the inside back wall of the eye. It works pretty much like the film in the back of a camera. It receives images formed by the optical parts at the front of your eyes, then instantly "develops" them and sends them on to the brain, which does the actual seeing. When the retinal "film" is damaged, vision is often impaired.

There are two types of retinopathy: background retinopathy, the milder form, and proliferative retinopathy, which is more serious. Neither type, on its own, is likely to cause any pain, but the proliferative form can lead to other eye problems that might cause pain.

What Happens in Background Retinopathy?

Background retinopathy generally progresses slowly, over many years. Its exact cause, or why it may later progress to proliferative retinopathy is not known. It seems to be related to the length of time you have had diabetes, and it is more common in insulin-dependent diabetes than in diabetes that can be controlled by diet or with oral medications.

Early changes are subtle and only slightly different from normal. There are usually no symptoms. Some of the retinal blood vessels gradually enlarge; some become irregular in size and develop some tiny weak spots (microaneurisms), which are the hallmark of this condition. They begin to leak exudates (fluid, fat, and protein) and blood. At first, depending on where leaks are located, they may affect vision only slightly and maybe not at all, but if they progress they are more likely to cause some reduction or distortion of vision.

The condition varies over time, sometimes getting better for a while and then worse, but tending to slowly worsen. As it advances, some of the smaller retinal blood vessels gradually become obstructed, resulting in a patchy loss of retinal nourishment. In some patients this leads to the development of proliferative retinopathy.

What Happens in Proliferative Retinopathy?

The name "proliferative retinopathy" comes from the new, abnormal blood vessels that begin to grow (proliferate) over the surface of the retina and optic nerve, the "cable" that transmits images from the eye to the brain. It is thought that they form in an attempt to nourish the areas of "starving" retina. Unfortunately, these blood vessels are fragile, and they frequently break and bleed. (The bleeding can cause a sudden appearance of floaters.)

If the bleeding is into the vitreous (the gel-like fluid in the center of the eye), vision can become clouded from the blood. At first the blood is rapidly absorbed, so vision tends to clear in a few weeks. But eventually, with re-bleeding, vision may not clear so rapidly or even at all. As more new blood vessels grow, the risk for more bleeding increases. Scars form and may tug on or even tear the retina, which can lead to a retinal detachment. All of these developments have the potential for leading to blindness.

Examination

As part of the history-taking, you will be asked how long you have had diabetes, how you are controlling it, and how well is it being controlled. You will have a complete vision examination, including a refraction with your pupils dilated (enlarged) with eyedrops. An ophthalmoscope will be used to study the interior of your eyes. The pressure inside your eyes will be checked with a painless test called tonometry. Depending on the type of tonometer used, you may be given anesthetic eyedrops.

Photographs may be taken of your retinas. Pictures are useful in determining the extent of the problem and evaluating its progression. If you have a test called fluorescein angiography, an orange-colored dye is injected into a vein in your arm. Then a rapid series of retinal photographs is taken as the dye travels through the eye's blood vessels. By identifying the position and extent of any abnormal blood vessels and any leakages, the angiogram provides important guidance for treatment.

Treatment

For background retinopathy or even for minimal proliferative retinopathy, you may not need any treatment other than keeping your diabetes under good control.

If the condition is threatening your vision, laser treatment may be recommended. Lasers are used in two different kinds of treatment: (1) "focal treatment," to stop retinal leakages, and (2) PRP (pan-retinal photocoagulation), to create hundreds of tiny burns in the retina that, by some unknown mechanism, reduce retinal swelling and congestion and the number of abnormally proliferating blood vessels, thus reducing the risk of internal bleeding. More than one series of laser treatments may be needed; all can be done on an outpatient basis and are usually painless.

Laser treatment may not help severe cases and sometimes lasers cannot be used at all, such as when the abnormal blood vessels, scars, and blood are too dense to let the laser beam shine through to the retina. Then, a major eye operation called vitrectomy may be suggested, to attempt removal of the scars and cloudy or bloody tissue. If this procedure is successful in clearing up the cloudy material inside the eyeball, laser treatment may then become possible.

Vision improvement does not always follow a vitrectomy, but when it does it can be dramatic. However, vitrectomy has a risk of serious complications, including more bleeding, retinal tears and detachment, so it is used only for the most advanced cases that are not otherwise treatable.

Diabetic retinopathy is one of the major causes of defective vision and blindness in our country today. If you have diabetes, make sure you have a thorough eye exam at least every year (more frequently in advanced cases), and you should always take the best possible care and control of your diabetes.