Eye Problems Linked to Diabetes

If you have diabetes, don't buy a new pair of glasses when you notice you have blurred vision. It could just be a temporary problem that develops rapidly and is caused by high blood glucose levels.

High blood glucose causes the lens of the eye to swell, which changes your ability to see. To correct this kind of blurred vision, you need to get your blood glucose back into the target range (90-130 milligrams per deciliter or mg/dL before meals, and less than 180 mg/dL one to two hours after a meal). It may take as long as three months after your blood glucose is well controlled for your vision to fully get back to normal.

Blurred vision can also be a symptom of more serious eye problems. The three major eye problems that people with diabetes may develop and should be aware of are cataracts, glaucoma and retinopathy.

Cataracts

A cataract is a clouding or fogging of the normally clear lens of the eye. The lens is what allows us to see and focus on an image just like a camera. Although anyone can get cataracts, people with diabetes get cataracts at an earlier age than most and the condition progresses more rapidly than in people without diabetes.

If you have a cataract, your eye cannot focus light and your vision is impaired. Symptoms include blurred or glared vision.

Treatment is usually surgery followed by placement of a lens implant, with glasses or contact lenses as needed to further correct vision.

Glaucoma

When fluid inside the eye does not drain properly from a build up of pressure inside the eye, it results in a disease called glaucoma. The pressure damages nerves and the vessels in the eye, causing changes in vision.

In the most common form of glaucoma, there may be no symptoms at all until the disease is very advanced and there is significant vision loss. In the less common form, symptoms can include headaches, eye aches or pain, blurred vision, watering eyes, halos around lights and loss of vision.

Treatment can include special eye drops, laser procedures, medicine or surgery. You can prevent serious problems by getting an annual glaucoma screening from your eye doctor.

Retinopathy

The retina is a group of specialized cells that convert light as it enters though the lens into images. The eye nerve or optic nerve transmits visual information to the brain.

Diabetic retinopathy is one of the vascular (blood-vessel related) complications related to diabetes. It is due to damage of small vessels and so is called a "microvascular complication." Kidney disease and nerve damage due to diabetes are also microvascular complications. Large blood vessel damage (also called macrovascular complications) includes complications like heart disease and stroke.

The microvascular complications have, in numerous studies, been shown to be related to high blood glucose levels. You can reduce your risk of these complications by improving your blood sugar control.

Diabetic retinopathy is the leading cause of irreversible blindness in industrialized nations. The duration of diabetes is the single most important risk for developing retinopathy. So the longer you have diabetes, the greater the risk. If retinopathy is not found early or is not treated, it can lead to blindness.

People with type 1 diabetes rarely develop retinopathy before puberty. In adults with type 1 diabetes, it is also rare to see retinopathy before 5 years duration of diabetes. The risks of retinal damage increase with progressive duration of diabetes. Intensive control of blood glucose levels will reduce your risks of developing retinopathy. The DCCT, a large study of people with type 1 diabetes showed that people with diabetes who achieved tight control of their blood sugars with either an insulin pump or multiple daily injections of insulin were 50%-75% less likely to develop retinopathy, nephropathy (kidney disease) or nerve damage (all microvascular complications).

People with type 2 diabetes usually have signs of eye disease when diabetes is diagnosed. In this case, control of blood sugar, blood pressure and blood cholesterol have important role in slowing the progression of retinopathy.

Types of Retinopathy:

• Background retinopathy. Sometimes the blood vessel damage exists, but there is no vision problem. This is called background retinopathy. It's important to carefully manage your diabetes at this stage to prevent background retinopathy from progressing to more serious eye disease.
• Maculopathy. In maculopathy, the person has developed damage in a critical area called the macula. Because this occurs in an area that is critical to vision, this type of eye problem can significantly reduce vision.
• Proliferative retinopathy. New blood vessels start to grow in the back of the eye. Because retinopathy is a microvascular complication of diabetes, a disease of small vessels, this type of retinopathy develops because of an increasing lack of oxygen to the eye from vascular disease. Vessels in the eye are thinned and occluded and they start to remodel.

Here, it is important to address the risks factors that can worsen the occluded vessels. Smoking cessation, hypertension control, cholesterol management and glucose control must take place in order to stop the progression of new vessels from forming into the orbit of the eye. These are fragile vessels that can bleed and eventually cause a clot to form in the orbit, which scars and causes detachment of the retina. This eventually leads to irreversible vision loss.

Treatment of diabetic retinopathy may involve laser procedures or surgery. In a study of people with diabetes with early retinopathy, laser therapy to burn the fragile vessel resulted in a 50% reduction of blindness.

To prevent retinopathy, have your eye doctor screen your eyes annually. Women with diabetes who later become pregnant should have a comprehensive eye exam during the first trimester and close follow-up with an eye doctor during the rest of their pregnancy. (This recommendation does not apply to women who develop gestational diabetes, since they are not at risk for retinopathy.)

How Can I Prevent Eye Problems?

The American Diabetes Association offers these eye care guidelines for people with diabetes:

• People with type 1 diabetes should have a dilated eye exam by an ophthalmologist or optometrist within 3- 5 years after diagnosis.
• People with type 2 diabetes should have a dilated eye exam by an ophthalmologist or optometrist shortly after diagnosis.
• Annually eye exams should be done on both type 1 and type 2 diabetes by an ophthalmologist or optometrist; more frequently if necessary.
• When considering pregnancy, women with a history of diabetes should have an eye exam prior and during pregnancy. This does not pertain to women with gestational diabetes.

In addition you should:

• Control your blood glucose
• Control high blood pressure

When to Contact Your Doctor?

Contact your doctor if any of the following occur:

• Black spots in your vision.
• Flashes of light.
• "Holes" in your vision.
• Blurred vision.

Get tips on how to control your diabetes.
View the full table of contents for the Diabetes Guide.

Reviewed by Certified Diabetes Educators in the Department of Patient Education and Health Information and by physicians in the Department of Endocrinology at The Cleveland Clinic.

Edited by John A. Seibel, MD, WebMD, December 2006.