Diabetes mellitus is a condition which impairs the body's ability to use and store sugar. Elevated blood-sugar levels, excessive thirst and urination, and changes in the body's blood vessels are all characteristic of the disease. Diabetes may affect vision by causing cataracts, glaucoma and most importantly, damage to blood vessels inside the eye.

What Is Diabetic Retinopathy?

Diabetic retinopathy, a complication of diabetes, is caused by changes in the blood vessels of the retina, the light-sensing nerve layer in the rear of the eye. These damaged blood vessels may leak fluid or blood, and develop fragile brush-like branches and scar tissue. The images which the retina sends to the brain become blurred, distorted or partially blocked.

The risk of developing diabetic retinopathy increases the longer a person has diabetes. About 80% of the people with at least a l 5-year history of diabetes have some blood vessel damage to their retina.

Diabetic retinopathy is particularly likely to occur at a younger age in juvenile diabetics, who have been diagnosed with the condition during their childhood or teenage years. Diabetic retinopathy is the leading cause of new blindness among adults in the United States, and people with untreated diabetes are said to be 25 times more prone to blindness than the general population. However, with improved methods of diagnosis and treatment only a small percentage of those who develop retinopathy experience serious problems with vision.

Types of Diabetic Retinopathy

Background retinopathy is an early stage of diabetic retinopathy. In this stage, fine blood vessels within the retina become narrowed or obstructed while others enlarge to form balloon-like sacs. These altered vessels leak blood and fluid, causing the retina to swell or form deposits called exudates. Sight is usually not seriously affected. It can, however, lead to more advanced sight-threatening stages, and for this reason is considered a warning sign.

In some cases, the leaking fluid collects in the macula, the portion of the retina responsible for detailed vision, such as reading. This problem is called macular edema.

Proliferative retinopathy describes the changes that occur when new, abnormal blood vessels begin growing on the surface of the retina or the optic nerve. These new blood vessels, called neovascularization, have weaker walls and may rupture and bleed into the vitreous, the clear gel-like substance that fills the center of the eye. This leaking blood can cloud the vitreous and partially block the light passing through the pupil towards the retina, causing blurred and distorted images. These abnormal blood vessels frequently grow scar tissue with them which may pull the retina away from its normal position at the back of the eye (detached retina). Abnormal blood vessels may also grow around the pupil (on the iris) causing glaucoma by increasing pressure within the eye. Proliferative diabetic retinopathy is the most serious form of diabetic retinal disease. It affects up to 20 YO of diabetics and can cause severe loss of sight, including blindness.

Cause and Symptoms

The cause of diabetic retinopathy is not completely understood; however, it is known that diabetes damages small blood vessels in various areas of the body. Pregnancy and high blood pressure may aggravate diabetic retinopathy.

Although gradual blurring of vision may occur if macular edema is present, sight is usually unaffected by background diabetic retinopathy and changes in the eye can go unnoticed unless detected by a medical eye examination. When bleeding occurs in proliferative retinopathy, the sight may become hazy, spotty or even disappear altogether. While there is no pain, this severe form of diabetic retinopathy requires immediate medical attention.

Detection and Diagnosis

A comprehensive medical eye examination and appropriate treatment by an ophthalmologist is the best protection against eye damage due to diabetic retinopathy. Serious retinopathy can be present without symptoms and improve with treatment. Therefore, people with diabetes should be aware of the risks of developing visual problems and should have their eyes examined regularly. (Periodic eye examinations are also advisable for apparently healthy people, because such examinations help detect the presence of diabetes and other diseases.)

To detect diabetic retinopathy, the ophthalmologist conducts a painless examination of the inner part of the eye using an instrument called an ophthalmoscope. The pupils may need to be dilated with eye drops.

If diabetic retinopathy is noted, the ophthalmologist may obtain color photographs of the retina. Sometimes a specialized technique is used which provides great detail about retinal blood vessels and leakage. First, a fluorescent dye is injected into a vein in the arm. The dye travels through the bloodstream, including the blood vessels of the retina. Photographs are taken in rapid succession as the dye passes through the retinal blood vessels. This technique, called fluorescein angiography, is often used by ophthalmologists to determine if further treatment is necessary.

Treatment

When diabetic retinopathy is diagnosed, the ophthalmologist considers the patient's age, history, lifestyle, and the degree of damage to the retina before deciding whether treatment or further observation of the disease is most appropriate. In many cases treatment is not necessary; in others it is recommended to halt the damage of diabetic retinopathy and improve sight wherever possible.

Laser Surgery

The most significant treatment is ophthalmic laser surgery, which seals or photocoagulates the leaking blood vessels. During this procedure, a powerful beam of laser light is focused on the damaged retina. Small bursts of the laser's beam seal leaking retinal vessels to reduce macular edema. When larger applications of the laser beam are scattered throughout more peripheral areas of the retina, the small laser scars reduce abnormal blood vessel growth (neovascularization) and help bond the retina to the back of the eye.

Laser surgery does not require an incision and may be performed in the ophthalmologist's office or an outpatient clinic. If diabetic retinopathy is detected early, photocoagulation by laser surgery retards vision loss. Even in the more advanced stages of the disease (proliferative retinopathy), it reduces the chance of severe visual impairment.

Other Treatments

If the vitreous is clouded by hemorrhage, laser photocoagulation cannot be used until the blood settles or clears. In some cases of persistent vitreous hemorrhage, cryotherapy of the retina, using local anesthesia and a cold instrument probe, may help shrink the abnormal blood vessels.

In advanced proliferative diabetic retinopathy, the ophthalmologist may recommend a vitrectomy. This is a micro surgical procedure, performed in the operating room, to remove the blood filled vitreous and replace it with a clear solution. About 70% of vitrectomy patients notice an improvement in sight after surgery.

The ophthalmologist may recommend a vitrectomy soon after the vitreous becomes clouded by blood, or may wait from several months up to a year to see if the blood clears on its own. Determining the most appropriate time to perform surgery depends on the extent of damage, as well as the condition of the other eye. If proliferative diabetic scar tissue detaches the retina from the back of the eye, severe sight loss or blindness can result unless surgery is performed to reattach the retina.

Successful treatment of diabetic retinopathy depends not only on early detection through medical eye examinations and treatment by an ophthalmologist, but also on the patient' s attitude and attention to medications and diet. Physical activity presents few problems to people with background retinopathy. Occasionally, some restriction in activity for patients with active proliferative retinopathy is recommended.

Who Can Treat Diabetic Retinopathy?

Only an ophthalmologist can treat diabetic retinopathy, one aspect of a major vascular disease affecting many parts of the body. An ophthalmologist is a medical doctor (MD or osteopath) especially educated, trained, and licensed to provide total care of the eyes. This care includes performing comprehensive eye examinations, prescribing corrective or protective lenses, diagnosing diseases and disorders of the eye, and applying the appropriate medical and surgical procedures necessary for their treatment.

Vision Loss Is Largely Preventable

Early detection of diabetic retinopathy is the best protection against loss of vision. It is important to remember that diabetic retinopathy may be present without any symptoms. People with diabetes should schedule examinations by an ophthalmologist at least once a year. More frequent medical eye examinations may be necessary once diabetic retinopathy has been diagnosed. In most cases, with careful monitoring, the ophthalmologist can begin treatment before sight is affected. Modern ophthalmic laser and operative surgical procedures are highly effective treatment for diabetic retinopathy. If you have additional questions or would like further information, contact your ophthalmologist.