Diabetes can cause a variety of eye diseases that can potentially lead to severe vision loss and even blindness. These diabetic eye diseases include diabetic retinopathy, cataract and glaucoma. Diabetic retinopathy is the most common eye disease in patients with diabetes.

1. What is diabetic retinopathy?
Diabetic retinopathy is damage to the light-sensitive inner lining of the eye called the retina. This damage is brought about by changes in the blood vessels of the retina due to elevated blood sugar.

Blood vessels damaged from diabetic retinopathy can cause vision loss in two ways. First, fluid can leak from the vessels leading to swelling of the retina, a condition known as macular edema. This can happen at any stage of diabetic retinopathy, but is more likely to occur as the disease progresses. Second, fragile abnormal blood vessels can develop and leak blood into the center of the eye, resulting in blurred vision. This is known as proliferative retinopathy. About half of the patients with proliferative diabetic retinopathy also have macular edema.

2. What are the symptoms of diabetic retinopathy?
During the early stages of diabetic retinopathy, patients may not have any visual problems. However, as the disease progresses, vision may start to deteriorate. Patients with more advanced diabetic retinopathy may also complain of spots floating in their vision. This may be a result of bleeding inside the eye due to damaged retinal blood vessels. An examination by an ophthalmologist (eye doctor) is necessary as more bleeding can occur. If left untreated, severe vision loss and even blindness can happen.

3. What are the different stages of diabetic retinopathy?
Diabetic retinopathy can be classified into two general stages based on the eye findings:

Nonproliferative Retinopathy.
In this stage of diabetic retinopathy, there is enlargement and increased tortuosity of the blood vessels. Microaneurysms, small balloon-like swelling of the retinal blood vessels, may also be seen. These changes to the retinal blood vessels result in edema or swelling of the retina. With the progression of the retinal edema, lipoprotein deposits begin to appear in the retina. As the disease worsens, some blood vessels that nourish the retina become blocked. This blockage deprives the retina of blood supply and oxygen. These areas of poorly oxygenated retina then send signals that stimulate the growth of new blood vessels for nourishment.

Proliferative Retinopathy.
At this stage, there is already the formation of new blood vessels. These vessels grow along the retina and along the surface of the transparent vitreous gel that fills the inside of the eye. By themselves, these blood vessels do not cause symptoms or vision loss. These new blood vessels, however, are very fragile and prone to leakage of blood. This leakage of blood is what results in severe vision loss and even blindness.

4. How is diabetic retinopathy diagnosed?
Diabetic retinopathy can be detected by having an ophthalmologist conduct a comprehensive eye exam. Several tests are done by the eye doctor to evaluate patients with a history of diabetes.

Visual acuity test. This test measures a patient’s distance vision through the use of an eye chart.
Tonometry. This test measures the pressure inside the eye. Anesthetiic eyedrops are place on the eye prior to doing this test.
Dilated eye exam. This examination allows the eye doctor to examine the retina thoroughly, looking for evidence of diabetic retinopathy. Eyedrops are placed on the patient’s eyes to dilate the pupils. These eyedrops can cause a temporary blurring of vision for a few hours. The ophthalmologist will then examine the inside of the eye to look for signs of diabetes such as:

• Leaking blood vessels
• Retinal swelling (macular edema)
• fat deposits on the retina
• bleeding (hemorrhages)
• new blood vessels
• blood vessel abnormalities
• retinal detachments

A fluorescein angiogram may be requested by the eye doctor to determine the severity of the diabetic retinopathy and/or to plan the laser treatment. In this test, a special dye (fluorescein) is injected into the blood vessel. Pictures of the retina are taken as the dye passes through the retinal blood vessels.

5. Who are at risk for diabetic retinopathy?
All patients with diabetes, whether type 1 or type 2, are at risk. The longer the duration of diabetes, the more likely a patient will develop diabetic retinopathy. Almost half of patients diagnosed with diabetes have some stage of diabetic retinopathy. It is important that diabetic patients get a comprehensive dilated eye exam at least once a year. Pregnant women with diabetes should also have a comprehensive dilated eye exam during their pregnancy.

6. How is diabetic retinopathy treated?
During the early stages of diabetic retinopathy, no treatment is necessary. However, to prevent the progression of diabetic retinopathy, people with diabetes should control their blood sugar levels, blood pressure, and blood cholesterol. In more advanced stages of diabetic retinopathy, such as proliferative retinopathy, laser treatment may be necessary. Laser treatment can help shrink the abnormal blood vessels growing in the retina. Laser treatment may also decrease the retina swelling. Several laser sessions are usually needed to complete the treatment. Some loss of peripheral vision, color vision and night vision may occur with laser treatment but this is a small price to pay in exchange for saving one’s vision. Laser treatment cannot restore vision that has already been lost.

If there is extensive bleeding or if there is a retinal detachment, a surgical procedure called vitrectomy may be necessary. In vitrectomy, the clear gel inside the eye that has been clouded with blood is removed and replaced with a salt solution. If the retina is detached, attempts are made to re-attach it and return it to its normal position. The general principle in treatment is that the earlier you receive treatment, the more likely will the treatment be effective. Laser treatment and vitrectomy have high success rates if done in a timely manner. Early detection and intervention is the best way to prevent vision loss.

7. What can I do to protect my vision?
Patients diagnosed with diabetes must have a comprehensive dilated eye exam at least once a year. This can be done by an ophthalmologist. Diabetic retinopathy, even in advanced stages like proliferative retinopathy, can develop without any symptoms. If you have already have diabetic retinopathy, you may need to have an eye exam more often than once a year. People with proliferative retinopathy can reduce their risk of blindness by 95 percent with timely treatment and appropriate follow-up care.

Research has shown that good blood sugar control slows the onset and progression of diabetic retinopathy. Diabetic patients with near normal blood sugar levels are also less likely to develop kidney and nerve disease. Other studies have shown that controlling elevated blood pressure and cholesterol can also reduce the risk of vision loss in diabetic patients. There is a very high risk for vision loss especially in the advanced stages. Early detection and timely treatment can prevent vision loss.

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