Diabetes and the Eyes

Dear Doctor Weaver,

Recently, I was diagnosed with diabetes and my family doctor recommended that I get an eye examination. Could you please explain?

Sincerely,
Felicia

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Dear Felicia,

Diabetes is a condition that affects your entire body. It is a result of the body not being able to regulate appropriate blood sugar levels, due to the poor production or deficient activity of insulin. Your doctor has probably explained to you the different types of diabetes, which are type 1 (insulin dependent) and type 2 (non-insulin dependent).

Those with type 1 require the use of insulin to modulate suitable blood sugar levels in the body. Individuals with type 2 typically have the ability to control their blood sugar levels by changing their lifestyle habits, by eating a healthy diet, losing weight and exercising. If the blood sugar levels are still high, oral medications would be used to control blood glucose.

The best way to see if your blood sugar levels are in the normal range is to see your family doctor for a physical evaluation. Your doctor would then order blood tests that would include a fasting blood glucose and hemoglobin A1c. The fasting blood sugar is taken in the morning, prior to eating anything that day. This is similar to the home-screening tests that diabetics have to monitor their blood sugar levels throughout the day. The fasting blood glucose shows how your body processed sugar from your diet the day before. The hemoglobin A1c provides greater information to the physician, for it shows how well your body processed glucose over the previous three months.

Uncontrolled blood sugar from diabetes can cause cardiovascular disease with an increased risk of stroke, neuropathy that can result in limb amputations, kidney failure, skin ulcerations, depression, ocular complications, as well as many other problems.

The most common ocular complication is fluctuating vision. If a patient has diabetes and comes in for an eye examination, it is important for his/her blood sugar levels to be normal and stable to get an accurate eyeglass prescription. If the patient had high or fluctuating blood glucose the time of the exam, his/her vision will change when the blood sugar level normalizes. Therefore, the eyeglasses prescribed during the eye exam would be useless.

More seriously, diabetes affects the eyes by causing the blood vessels in the retina to become “leaky.” Early changes in the retina from diabetes would include microaneurisms and very small, pinpoint hemorrhages, called diabetic retinopathy. These signs usually resolve in time, and do not progress as long as the blood glucose is maintained at normal and stable levels. If the blood sugar remains high or fluctuates, the blood vessels can allow even more fluid to escape, which can cause retinal edema that can potentially result in vision loss or even blindness. These advanced changes in the retina would require co-management with a retinal specialist for treatment.

Diabetes can also accelerate the formation of cataracts as well. If you remember from a previous article, cataracts cause decreased vision as well as light sensitivity problems, such as haloes and glare. If glasses or contact lenses no longer provide clear, crisp vision, cataract surgery would be recommended.

High uncontrolled blood sugar levels can also cause the formation of new “leaky” vessels in a process called neovascularization. The vessels can grow in different parts of the eye. If in the retina, they can contribute to fluid accumulation or large hemorrhages in the retina. The neovascularization can also occur in the iris and in the angle, the drainage area of the eye. This will raise the intraocular pressure and cause neovascular glaucoma, which is a severe form of glaucoma that can lead to blindness.

It is advised for those with diabetes to have an annual dilated eye examination to monitor for any ocular changes related to this disease. It is possible that many of these signs can occur with no symptoms experienced by the patient, so it is important to seek routine care with your eye doctor and family physician to ensure that diabetes is diagnosed and treatment is initiated when necessary.