written by Dr. William McSwain

Diabetes is the leading cause of blindness in the United States among people age 20 – 64. It is an especially disabling disease because it tends to affect working age people who often have families depending on them. In people with diabetes, elevated blood sugar causes damage to the small blood vessels throughout the body. This damage is particularly prevalent in the kidneys, nervous system, and eyes. Diabetes primarily causes vision loss through diabetic retinopathy and diabetic macular edema, but can also cause glaucoma and worsening of cataracts.

In diabetic retinopathy, the small blood vessels that supply the retina become damaged resulting in bleeding or leakage that distorts vision. In advanced stages, referred to as proliferative diabetic retinopathy, abnormal blood vessels grow across the retina and contract leading to retinal scarring, vitreous hemorrhage, and retinal detachment. These abnormal blood vessels may block the drainage system in the front of the eye leading to increased eye pressure and damage to the optic nerve from glaucoma.

Diabetic macular edema is swelling of the macula, the portion of the retina responsible for central vision. This interferes with tasks requiring fine detailed vision such as reading, driving, or recognizing faces.

You may notice your vision becomes blurry whenever your blood sugar is elevated. This is because elevated blood sugar causes the lens inside your eye to swell which can temporarily alter your glasses prescription. If your blood sugar is elevated while you are having your glasses prescription checked, alert us because this may cause errors in measurement. Over time, repeated swelling can cause opacification or clouding of the lens resulting in a cataract.

The diagnosis of diabetic eye disease involves a combination of the patient history, dilated exam, and testing including high definition photography, optical coherence tomography (OCT), and fluorescein angiogram (FA). Photos of the retina are taken at your initial appointment to monitor for future progression.

The most important factor in preventing vision loss or blindness from diabetes is maintaining strict control of blood sugar. Control of your blood sugar is completely out of my hands and is up to you and your diabetes doctor. You can dramatically decrease your risk of vision loss by following the recommendations your diabetes doctor makes about diet, exercise, or weight loss and adhering strictly to your medication regiment. Your primary care doctor can also manage other conditions that contribute to diabetic eye disease like high blood pressure or anemia (low red blood cells).

The second most important factor in preventing vision loss is early detection. All diabetics should have a comprehensive dilated eye exam with an ophthalmologist at least once a year. It is much easier to treat diabetic eye disease and prevent vision loss if it is diagnosed at an earlier stage. Ideally, diabetic eye disease should be diagnosed and treated before you develop any vision loss, so please follow up at all your appointments even if you are not having any symptoms. If diabetic eye disease is progressing, available treatments include scatter laser, focal/grid macular laser, intravitreal injections, and vitrectomy.

Scatter laser, also known as panretinal photocoagulation (PRP), involves making 1,000 to 2,000 tiny burns in the peripheral retina. These burns cause the abnormal blood vessels to shrink. This protects your central vision in the macula but may cause decrease night and peripheral vision. Focal/grid macula laser is similar to PRP, but involves treatment of leaking blood vessels and swelling in the macula.

Intravitreal injections are an injection into the vitreous, the jelly-like substance in the back of the eye. These injections often need to be repeated on a regular basis. You will be given anesthetic prior to the injection to make it as pain-free as possible. The injection only takes a few seconds and is done with a very small needle. After the injection, your vision may be decreased but should recover in the next 1-2 days. Your eye may appear red or have a small spot of bleeding at the injection site, but this should clear in a few days. You may notice black swirls in your vision for a few weeks caused by the medication floating in the vitreous jelly.

Occasionally, the abnormal blood vessels may hemorrhage resulting in bleeding that disrupts vision. If this bleeding does not clear on its own, a vitrectomy may be indicated. A vitrectomy involves surgical removal of the vitreous, blood, and abnormal blood vessels to clear your vision.

ADDITIONAL READING: https://nei.nih.gov/health/diabetic