Diabetes and Eye Health
What to know about the disease’s association with vision loss
En español | Not paying attention to your blood sugar can lead to a lot more than some high digits on your bathroom scale. There’s a laundry list of health complications that come from lofty glucose levels — among them, nerve damage in your hands and feet, kidney damage, heart disease and stroke. And then there are your eyes. People who have diabetes — Type 1 or Type 2 — are at risk for a disease called diabetic retinopathy, in which consistently elevated blood-sugar levels damage the blood vessels in the retina, the thin layer of tissue located in the back of your eye.
Diabetic retinopathy is sneaky. In its early stages, you may not even know you have it. But as it worsens, your vision takes a hit. It may fluctuate between clear and blurry. You may get floaters (spots or dark strings in your vision), poor night vision, dark or empty areas in your vision, or colors that appear faded. Left unchecked, it can lead to vision loss. In fact, diabetic retinopathy is the most common cause of vision loss among people with diabetes and is the most frequent cause of new cases of blindness among adults ages 20 to 74.
All the more reason to learn everything you can about this alarming — but preventable — disease.
How the disease progresses
The early stage of the disease is called nonproliferative diabetic retinopathy (NPDR), and its most common form. With NPDR, tiny blood vessels leak blood or other fluids into the retina, causing it to swell, sometimes leading to changes in your vision. NPDR can sometimes trigger a condition known as macular edema, in which the area in the center of the retina — responsible for your straight-ahead vision — begins to swell from a buildup of fluid and thicken. Vision can get blurrier or look a little bit off. If left untreated, chronic macular edema can lead to irreversible damage.
As NPDR progresses, those damaged blood vessels close off and lose their ability to channel blood to the retina, depriving it of the oxygen it needs to do its job.
This leads to the most advanced — and dangerous — stage of the disease, known as proliferative diabetic retinopathy (PDR), in which new blood vessels start growing along the inside of the retina, but don’t develop properly. “They’re often very fragile and can burst,” says Rahul Khurana, M.D., an associate clinical professor in ophthalmology at the University of California San Francisco Medical Center and a spokesperson for the American Academy of Ophthalmology. “If the eye fills with blood, you can lose your vision immediately and it can be pretty dramatic.” (Imagine dark food coloring that has been squirted into a clear glass filled with water.)
What’s more, these new blood vessels can cause other complications. For example, they sometimes develop scar tissue, which can contract and pull on the retina, causing it to detach from underlying tissue.
If you have mild or moderate NPDR, you may not need treatment right away, though your ophthalmologist will closely monitor your eyes for any changes. Keeping your blood sugar in check can usually halt the progression and curb vision loss, and sometimes can even restore some of your vision.
Watching those blood pressure numbers is also crucial. Over time, hypertension can damage those fragile blood vessels in the retina, making matters worse. “Imagine a garden hose that is weak and leaking,” explains Omesh P. Gupta, M.D., an ophthalmologist and retina specialist at Wills Eye Hospital in Philadelphia. “When your blood pressure is high, it’s like turning up the faucet, so the hose starts leaking even more severely.”
If you’ve reached the point where medical intervention is necessary, know this: “Over the past 10 to 15 years,” says Gupta, “the treatment of diabetic retinopathy has been radically improved.”
The type of treatment depends on the cause of vision loss. Diabetic macular edema used to be treated with lasers to prevent the condition from worsening. Now, though, a specific class of medicines, anti-vascular endothelial growth factor (VEGF) drugs administered as an injection into the side of the eye, has revolutionized care. They work by blocking the protein that can stimulate those abnormal blood vessels to grow. “Not only can we prevent patients from losing their vision, some patients can actually improve their vision,” says Khurana. VEGF injections also are being used to prevent NPDR from progressing into the advanced form of the disease.
By the way: If the idea of having something injected into your eye makes you squirm — relax. “It can sound very scary,” admits Gupta. “But the vast majority of patients find the procedure comfortable once the eye is numbed properly.”
For PDR there are three main types of treatments. The first involves panretinal photocoagulation laser treatment, which involves making thousands of tiny laser burns to help shrink the new, abnormal blood vessels and possibly prevent them from growing again. Usually done in your ophthalmologist’s office or at an eye clinic, laser treatments are typically completed in one session, though some people may need more. Your vision will be blurry for about a day after the procedure.
Another possible option: “We’ve also discovered that those same injections we’re using to treat diabetic macular edema can also cause the new, abnormal blood vessels to go away, so doctors are starting to use them for that,” says Khurana.
If injections or lasers aren’t working or doing enough, your ophthalmologist may suggest a vitrectomy, a surgical procedure that can tackle an array of vision-threatening complications — including clearing out blood from the retina and treating the underlying cause of the bleeding, as well as putting a detached retina back into place.
While game-changing procedures are reassuring, your smartest move is to be proactive, keeping both your eyes and body in good shape, thus avoiding the need for medical intervention altogether. “One thing we do know is that the longer you have your diabetes, and the less controlled your blood sugar is, the more likely you are to develop this disease,” says Khurana. He says it’s important that patients with Type 1 diabetes have annual screenings five years after the onset of their disease. Patients with Type 2 should have a prompt examination at the time of diagnosis, and at least a yearly examination.
“Nearly 40 percent of Americans who have diabetes are not getting a dilated eye examination, and that’s a big problem,” Khurana adds. “We know that 95 percent of vision loss from diabetes can be prevented, but that can only happen if we examine patients early.”