This is our final discussion about diabetes and diabetic eye disease.
We have now reviewed non-proliferative diabetic retinopathy, proliferative diabetic retinopathy, and diabetic macular edema. Our discussion has been focused on the retina. Now, we will turn to other structures of the eyes that can be affected by diabetes.
Cornea
The cornea can develop several problems due to diabetes and high sugars. One is swelling of the cornea. This can lead to problems wearing contact lenses or blurry vision. Another is delayed wound healing. It can take longer for the cornea to heal after getting a scratch or infection. There can be long-term damage with these when non-diabetic patients do not usually have any damage. This can include scarring and vision changes. People with diabetes also have loss of sensation in the cornea. This can make it easier to get a scratch in the eye or have something in it and not feel as much discomfort. Lastly, there can be changes in the tear film which can lead to dry eye symptoms.
All of these conditions can be found with a comprehensive eye exam. They can cause blurry vision, the feeling of something in the eye, or eye discomfort. It is important to see a doctor with any irritation as many cases require treatment with medicated eye drops.
Lens
Diabetes can affect the lens in two major ways.
The first is directly from an increase in blood sugars. When the sugar levels are high in the body, the lens will also fill with more sugar. This causes the lens to fill with more water to balance the increase in sugar. The lens must change its shape to accommodate these extra substances. This causes blurry vision and may cause a change in a person’s glasses or contact lens prescription. This usually improves by lowering the blood sugar. If necessary, a person can change their glasses or contact lenses to help with the vision.
The second is called a cataract. Proteins break down in the lens and begin to form a cataract. This process is normal as a person gets older, but the process can be accelerated in patients with diabetes. Cataracts can cause blurry vision, glare with bright lights, cloudy vision, and difficulty with night vision.
If the cataract is not very bothersome, it can be left alone. If it is causing blurry vision, glasses or contact lenses are attempted. If these are not helping or the cataract is too advanced, surgery is required to remove it. When surgery is done, a new lens is put in the place of the cataract that was removed. This lens has a prescription built into it that allows the patient to see.
Optic Nerve
We discussed that proliferative diabetic retinopathy can affect the optic nerve and iris by causing the growth of abnormal blood vessels. When the new blood vessels block the normal path of fluid flow in the eye, one can develop a specific type of glaucoma called neovascular glaucoma. Glaucoma is a condition that causes damage to the optic nerve and subsequent vision loss. A comprehensive exam is necessary to diagnose glaucoma. Several tests are done in the clinic to determine how advanced it is. Since this type of glaucoma is caused by the abnormal blood vessels from uncontrolled diabetes, the diabetes needs to be treated (using laser and injections). The glaucoma can be treated with eye drops, laser, and/or surgery.
The nerve can also become swollen in patients who have diabetes. Diabetic papillopathy is a benign condition that resolves on its own and does not usually cause long term vision loss. Optic neuropathy on the other hand can lead to vision loss. Patients with diabetes are at higher risk of developing this condition and it is difficult to treat.
Extraocular Muscles
The nerves that control the eye muscles can also be affected by diabetes. They can become temporarily paralyzed, called a nerve palsy. The most common is the nerve that controls the lateral rectus muscle. This pulls the eye out and allows one to look toward the ear. If it is affected, the nerve does not work well, and the muscle cannot turn the eye outward. Patients present with the eye turned toward the nose. Since diabetes affects the blood vessels, it can cause small injuries to the vessels that provide nutrients to these nerves and muscles.
Patients usually present with double vision. On exam, doctors will measure the amount that the eye is turned. Since this is usually due to diabetes or high blood pressure, controlling these two things will help to resolve the double vision and allow the nerve to work properly. If the condition does not resolve on its own after a few months, special glasses can be prescribed to account for the poor muscle movements. There are also surgical procedures that will relax or tighten the muscles to turn the eye back to normal.
As we have discussed before prevention is extremely important to avoid these consequences of diabetes. A dilated comprehensive exam should be done once a year to look for changes from diabetes and more often if changes are detected. Controlling sugar, blood pressure, and cholesterol all help to reduce the risk of developing eye disease and vision loss. Losing weight and stopping smoking will also help.
Return next month for a discussion on a new topic!