Diabetic Eye Disease Overview

Diabetes mellitus is one of the leading causes of irreversible blindness worldwide, and, in the United States, it is the most common cause of blindness in people younger than 65 years.

In addition to being a leading cause of blindness, diabetic eye disease encompasses a wide range of problems that can affect the eyes.

• Diabetes mellitus may cause a reversible, temporary blurring of the vision, or it can cause a severe, permanent loss of vision.



• Diabetes mellitus increases the risk of developing cataracts and glaucoma.

Some people may not even realize they have had diabetes mellitus for several years until they begin to experience problems with their eyes or vision. Severe diabetic eye disease most commonly develops in people who have had diabetes mellitus for many years, but they have had little or poor control of their blood sugars over that period of time.

Diabetes mellitus may also result in heart disease, stroke, kidney failure, and circulatory abnormalities of the legs.

With the recent release of a more accurate definition of diabetes mellitus by an international expert committee of the American Diabetes Association, an estimated 41 million people in the United States (40% of adults aged 40-74 years) have "pre-diabetes," a condition that significantly increases their risk for developing diabetes.

This new definition underscores the importance for you to take steps to help prevent your development of this disease. You can try to avoid the problems associated with diabetes mellitus, including those that affect the eyes, by taking appropriate care of yourself:

• Watch your diet
• Maintain a healthy weight
• Participate in an exercise program
• Do not smoke

If you have already been diagnosed with diabetes mellitus, you should also do the following:

• Monitor your blood sugars and your glycosylated hemoglobin (Protein in the red blood cells that carry oxygen is called hemoglobin. Glycosylated hemoglobin is hemoglobin that has bonded to blood sugar).
• Take your diabetes medications as prescribed

Diabetic Eye Disease Causes

Over many years, high blood sugar and other abnormalities in metabolism found in people with diabetes mellitus may damage the blood vessels in the body. This damage to the blood vessels leads to poor circulation of the blood to various parts of the body. Since the function of the blood is to carry oxygen and other nutrients, this poor circulation causes decreased oxygen delivery to tissues in different parts of the body and subsequent damage to those tissues.

Some of the most sensitive tissues to decreased blood flow and oxygen delivery include the brain, the heart, the kidneys, and the eyes. Lack of adequate oxygen delivery to these areas causes strokes, heart attacks, kidney failure, and vision loss.

The feet and the lower legs can also suffer from poor blood circulation and oxygen delivery, resulting in symptoms of numbness and tingling; poor healing of even minor wounds; ulceration and infection; and, not infrequently, the need for amputation of a toe, a foot, or the lower leg.

The primary part of the eye affected by diabetes mellitus is the retina.

The retina can be thought of as the film in a camera. If the film in a camera is faulty, the resulting picture will be blurry. In a similar manner, if the retina is swollen, wrinkled, or otherwise structurally damaged, the vision in that eye will be blurry. Depending on the type and extent of damage in the retina, the change in vision will range from minimal to severe and be temporary or permanent.

• In people with diabetes mellitus, changes in the walls of the small blood vessels in the retina are caused by blood sugar abnormalities. These small blood vessels may begin to "balloon," forming what are called microaneurysms, as well as leak fluid (called edema) and blood (called dot and blot hemorrhages) into the retina. This process is called background diabetic retinopathy or nonproliferative diabetic retinopathy. If fluid accumulates in the central part of the retina (called the macula) and causes swelling there, the process is called diabetic macular edema.



• As a response to decreased oxygen delivery to the retina, new blood vessels may begin to grow, a process called proliferative diabetic retinopathy. Although new blood vessels may sound like a good thing, considering that the old blood vessels are damaged, the new blood vessels are actually more harmful than beneficial. The new blood vessels are extremely leaky and fragile, leading to bleeding inside the eye (called vitreous hemorrhage) and usually resulting in severe vision loss. If not treated appropriately, this vision loss may be permanent.



• If the new blood vessels are extensive, they may cause scarring inside the eye, resulting in tractional retinal detachments, which is another cause of permanent vision loss.



• In cases of severe proliferative diabetic retinopathy, new blood vessels may grow on the surface of the iris, causing neovascular glaucoma, a particularly severe form of glaucoma.



• Many people with diabetes mellitus may notice that their vision becomes blurry when they have fairly large, rapid shifts in their blood sugar levels. This temporary blurring is because the sugar in the blood can diffuse into the lens of the eye and cause it to swell, thus changing the focal point of the eye and resulting in blurring of the vision. Over time, this swelling is thought to damage the lens and cause it to become cloudy, resulting in a cataract.



• The high blood sugar levels may also eventually damage the cells lining the trabecular meshwork toward the front of the eye, where the fluid (called aqueous humor) flows out from within the eye. When these cells are damaged, the trabecular meshwork cannot function correctly. If the trabecular meshwork does not function correctly, the fluid cannot flow out of the eye properly and the pressure inside the eye can increase. This high pressure inside the eye can damage the optic nerve and cause permanent vision loss. This process is called glaucoma.

Diabetic Eye Disease Symptoms

If you have fairly large, rapid shifts in your blood sugar levels, you may notice that your vision becomes blurry. This may occur prior to the diagnosis of diabetes mellitus, or it may develop after the initiation of treatment or a change in treatment of diabetes mellitus.

The sugar in the blood can diffuse into (or out of) the lens of the eye and cause it to swell (or shrink), thus changing the focal point of the eye and resulting in blurring of the vision. This difficulty with vision or focusing will disappear once blood sugar levels have been stable for a few days.

• Even if you have background diabetic retinopathy or early proliferative diabetic retinopathy, it is possible that you may not have any symptoms, or you may experience mild-to-severe blurring or vision loss. Many people with severe diabetic eye disease may not realize that they have a vision problem until it is too late and permanent damage has already occurred.



• If you have a cataract, your vision may become blurry or hazy. At night, you may experience glare from oncoming lights.



• If you have glaucoma, you may not experience any symptoms until a significant loss of vision has already occurred.

When to Seek Medical Care

Even if you are not experiencing any symptoms due to your diabetes mellitus, you should have an annual eye examination by an ophthalmologist (a medical doctor who specializes in eye care and surgery).

If your ophthalmologist notices any significant signs of diabetic eye disease or if you require treatment, you may need to be examined more frequently.

If you note any significant changes in your vision other than a mild temporary blurring, you should contact your ophthalmologist immediately.

Diabetic Eye Disease Treatment

Self-Care at Home

If you watch your diet, perform your exercise routine, monitor your blood sugars, and take your diabetic medications, the chances of developing serious problems due to diabetes mellitus decrease dramatically.

If you have diabetic eye disease and are experiencing serious visual problems, almost all your treatment requires the care provided by an ophthalmologist.

Medical Treatment

Medical treatment of diabetic eye disease is generally directed at the underlying problem - the diabetes itself. The better control you have of your diabetes, the fewer problems you will have in the long run.

Monitoring your glycosylated hemoglobin (hemoglobin A1C, Hb1AC) is the best assessment of the overall level of blood sugar control. Your medical doctor will order this blood test at least once a year. If your result is initially found to be abnormal or if your self-test blood sugar results become more variable, then this blood test may be ordered more frequently.

• For diabetic retinopathy, temporary use of corticosteroids or other medications, in the form of either eyedrops or injections, may be used to decrease leakage from the blood vessels, but their use is rare. Surgical treatment (ie, laser treatment) is the treatment of choice.



• Cataracts are commonly treated with cataract surgery.



• Glaucoma requires the use of antiglaucoma medications.

Prevention

If you have diabetes mellitus, "an ounce of prevention is worth a pound of cure." If you watch your diet, perform your exercise routine, monitor your blood sugars, and take your diabetic medications, the chances of developing serious problems from diabetes decrease dramatically.

Even if you have not been diagnosed with diabetes mellitus, watching your diet, maintaining a healthy weight, participating in an exercise program, and not smoking are advisable. This is especially important in light of the new, more accurate definition of diabetes mellitus that estimates 41 million people in the United States have "pre-diabetes," a condition that significantly increases the risk for developing this disease.