Protecting Your Eyes from Complications of Diabetes

Did you know that people with diabetes who have high levels of sugar (also known as blood glucose) for a long time can experience damage to the large and small blood vessels in the body? The large blood vessels that may be damaged include those in the heart, brain, and legs. This damage may lead to heart attack, stroke, and poor blood flow in the legs. The small blood vessels that may be damaged include those in the feet, kidneys, and eyes. This damage may lead to a tingling in or loss of the feet or toes, kidney damage, and vision loss.

This damage to the blood vessels in the retina is referred to as diabetic retinopathy. It occurs in 4 of every 10 people with diabetes. It is the most common cause of adult blindness in the United States.

What Is Diabetic Retinopathy?

Diabetic retinopathy is a condition that may cause damage to your eyes and lead to vision loss. It can happen in anyone who has diabetes. In general, the longer the duration of diabetes, the more likely it is to occur. Diabetic retinopathy damages the retina (see Figure 1). The retina is like the film in a camera that takes snapshots of what you see. Without the retina, you would not be able to see.

How Does Diabetic Retinopathy Damage Your Vision?

There are 2 stages of diabetic retinopathy: (1) nonproliferative and (2) proliferative.

In the first stage, nonproliferative diabetic retinopathy, high glucose levels hurt the walls of the small blood vessels in the retina (Figure 1) and cause them to leak fluid. This leakage of fluid can cause macular edema (or swelling of the retina), which can lead to vision loss. Blood vessels can also become blocked, preventing oxygen from reaching areas of the retina. A blockage of the oxygen supply to the retina can eventually result in vision problems.

In this stage, your diabetic retinopathy could be mild, moderate, or severe. As your condition progresses, the severity of the disease increases.

• Mild?Blood vessels swell slightly in your retina.
• Moderate?There is more swelling of the blood vessels in your retina, and the vessels begin to leak into the retina and close off and collapse.
• Severe?All of the above problems spread over more of the retina.

In the second stage, proliferative diabetic retinopathy, many blood vessels in the retina have closed off. To make up for the low level of oxygen, the retina makes new small blood vessels. Unfortunately, these new vessels are spider web-like, thin, and brittle, and they may break easily. If the new blood vessels break, blood leaks into the retina, causing more blurring of vision. To stop the bleeding, the body forms scar tissue. Scar tissue further impairs vision and may lead to severe vision loss or permanent blindness. The retina also may detach.

Both stages of diabetic retinopathy can harm your vision a great deal. In order to prevent more vision loss, the condition must be caught early.

What Are Symptoms of Diabetic Retinopathy?

Diabetic retinopathy can occur in patients with type 1 or type 2 diabetes. Patients with diabetic retinopathy often have no warning signs of vision loss. The condition can be diagnosed by your eye doctor using special equipment. You should see your eye doctor at least once a year. If you have any of the following symptoms, however, you should contact your health care provider right away:

• Blurred or cloudy vision
• Pain or pressure in one or both eyes
• Seeing double
• Redness in the eyes that does not go away
• Tunnel vision (restricted field of vision)
• Seeing "floaters," "black spots," "cobwebs," or "flashing lights" in your vision (see Figure 2)
• Straight lines that do not look straight
• Difficulty seeing in dim light

If your vision appears like the second picture in Figure 2, you may have diabetic retinopathy.

How Can Diabetic Retinopathy Be Prevented?

Your health care provider will tell you what your goal levels should be for glucose, blood pressure, and cholesterol. According to the American Diabetes Association, a fasting (meaning without eating) blood glucose up to 100 mg/dL is considered normal. Levels between 100 and 126 mg/dL usually mean impaired fasting glucose, or prediabetes. Diabetes is usually diagnosed when fasting blood glucose levels are 126 mg/dL or higher. Keeping your blood sugar at 100 mg/dL or less may reduce your chance of developing diabetic retinopathy. Some patients, even with the best blood sugar control, may still develop diabetic retinopathy. That is why it is very important to schedule regular visits with your eye doctor.

Your eye doctor will perform a comprehensive eye examination that includes the following tests to catch diabetic retinopathy early:

• Visual acuity test?Your eye doctor will have you read a series of large and small letters and numbers to see how clearly you can see.
• Dilated eye exam?Your eye doctor will place special drops in your eyes to make the pupil open very wide. These drops help your eye doctor see the back of your eye better to check for signs of diabetic retinopathy. Your eyes may be sensitive to light after the drops are given, and you may want to wear sunglasses until your eyes return to normal.

Your eye doctor may also test the pressure inside your eyes or create images of your eyes using special equipment.

If you have diabetes and are planning to become pregnant or are pregnant, it is important to have a comprehensive eye exam before and during pregnancy.Your eye doctor should follow you closely until you have your baby.

How Can Diabetic Retinopathy Be Treated?

The best treatment for diabetic retinopathy is prevention. Good diabetes management can help reduce the risk of diabetic retinopathy and its progression. It can be treated by the following methods:

• Scatter laser treatment?A laser is a powerful beam of light. During scatter laser treatment, thousands of beams are scattered throughout the retina to stop the growth of new blood vessels.
• Focal laser treatment?During focal laser treatment, beams of light are used in focused areas of the retina to seal leaks. Some patients may experience some slight anxiety or discomfort.
• Vitrectomy?This procedure involves removal of part or all of the vitreous to get rid of blood or scar tissue that may block vision. The vitreous fluid (Figure 1) normally is clear and gel-like and fills the center of the eye. If the vitreous becomes dark and cloudy, a vitrectomy may be needed.

How Can the Pharmacist Help?

Your pharmacist can recommend sight-saving tips, such as achieving and maintaining acceptable glucose, blood pressure, and cholesterol levels through the correct use of medications on a daily basis. Your pharmacist will educate and counsel you about your medications, about the importance of regular diet and exercise, and about keeping regular eye doctor appointments. Your pharmacist may assist in communicating with your eye doctor if you are noticing any changes in your vision.

Dr. Throm is an assistant professor of pharmacy practice at Midwestern University College of Pharmacy-Glendale, Glendale, Ariz.