How Diabetes Affects Your Eyes

Most of us think of diabetes as a blood sugar disease.

It’s actually not.

“What I tell patients is to think of diabetes as a blood vessel disease and in terms of blood vessel damage,” said Dr. Julian Nussbaum, chair of the Department of Ophthalmology at the Medical College of Georgia and a retinal specialist at the Augusta University Health Eye Center. “During periods where there’s extra blood sugar lying around, not all of it goes out in urine. It stays in the body, where it’s converted to material that acts like poison to small blood vessels.”

The eye in particular is rich in these tiny vessels, called capillaries. “It can take up to five to 10 years to see damage,” he continued. “It all occurs at a microscopic level.”

The Retina: A Blood Vessel Problem

When blood vessels leak into the retina, the retina can swell like a sponge. If the swelling affects the central retina known as the macula, then that is known as macular edema, which if untreated, can lead to irreversible vision loss.

If enough of these blood vessels are damaged, then the retina becomes starved for oxygen and the essential nutrients that it needs. The retina then tries to repair the damage by growing new blood vessels. That sounds like a great idea, but those new vessels can start to grow out of control, starting a process called proliferative diabetic retinopathy (because of the proliferation of these abnormal vessels). These vessels are fragile and can break and bleed at any time. In addition, they can bring along a scaffolding of tissue to grow on that can contract and pull on the retina, producing a retinal detachment. Once this proliferative process starts, blindness can happen as little as 18 months.

While the blood vessel damage can’t be reversed, “Our goal in the treatment of this disease is to catch changes early enough so that we can stop its progression,” said Nussbaum.

Treatment of diabetic retinopathy includes the use of medications that stop the retinal vessels from leaking and producing abnormal new vessels, and laser treatments to rebalance oxygenation in the retina. If severe bleeding and scarring occurs, with detachment of the retina, surgery may also be needed.

Cataracts and Diabetes

When blood sugars run high, diabetics might notice some blurriness in their vision as the lens of their eyes swell. That blurriness usually goes away when sugars get back in control and the lens shrinks. But when that happens over and over again, the lens can start to become opaque, a condition known as cataracts. Cataract symptoms include blurred vision, halos around lights, reduced night vision and greater sensitivity to glare.

“Cataracts are more common in diabetics, and they may get them earlier in life,” said Nussbaum. “To fix it requires cataract surgery and replacement of the lens.”

Glaucoma: High Pressure

It’s well known that diabetes can double a person’s risk of developing glaucoma, a disorder where increased pressure in the eye damages the optic nerve, causing blindness.

It is believed that diabetes over time leads to an accumulation of material ultimately affecting the drainage channels toward the front of the eye. “Fluid is produced and drained constantly in the eye,” said Nussbaum. “It helps maintain volume, it cools, and it provides nutrition to the cornea.”

But too much fluid builds up pressure, which leads to glaucoma. While certain glaucomas can cause eye pain, for the most part, it’s a silent disease that gradually chips away at vision over time. Treatment ranges from eye drops or medications that help relieve eye pressure or laser and other surgery.

What You Can Do

“The best advice we can give patients is to tightly control their diabetes,” said Nussbaum.

Tight control means that those with type 1 or type 2 diabetes keep hemoglobin A1C levels at 7 percent or less.

And because many diabetic eye diseases don’t have early symptoms, that annual eye exam is also a must. “The good news is that if you maintain good control of your blood sugar and your blood pressure, and you undergo your annual eye evaluation, even if you do develop some eye disease, there is far less risk of vision loss or blindness,” said Nussbaum.