Diabetic retinopathy, damage to the retina of the eye caused by high blood glucose, is the leading cause of new cases of blindness among people ages 20-74 in developed countries. There are several types of treatment for diabetic retinopathy, but the best approach is early detection and treatment, which can reduce the risk of blindness by 95%.
What causes it
The retina is the light-sensitive tissue at the back of the eye. It detects light and sends signals that travel to the brain by way of the optic nerve to create the images that we see. Chronically elevated blood glucose levels associated with poorly controlled diabetes gradually damage the tiny blood vessels in the retina. The damage causes these vessels to leak fluid or bleed, distorting vision. In advanced cases, new, abnormal blood vessels grow (or “proliferate”) on the surface of the retina, which can cause scarring in the retina.
Diabetic retinopathy may progress through four distinct stages. In the first stage, known as mild nonproliferative retinopathy, the tiny blood vessels of the retina develop swellings, or microaneurysms, which leak fluid into the retina. In the second stage, called moderate nonproliferative retinopathy, the vessels that supply blood to the retina may become swollen or distorted, and may lose their ability to transport blood. Both of these conditions can change the appearance of the retina and may contribute to the development of diabetic macular edema (DME). (See the sidebar “What Is Diabetic Macular Edema?” for more information.) In the third stage, severe nonproliferative retinopathy, more blood vessels become blocked, and the areas of the retina that are deprived of blood begin to secrete growth factors, which stimulate the growth of new blood vessels in the retina. In the fourth stage, proliferative diabetic retinopathy, new blood vessels begin to grow along the surface of the retina and sometimes into the vitreous gel, the fluid that fills the inside of the eye. These fragile new blood vessels may leak and bleed, and the resulting scar tissue can contract and cause retinal detachment, in which the retina pulls away from its underlying tissue, which may lead to permanent vision loss.
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What Is Diabetic Macular Edema?
The macula is a region of the retina responsible for straight-ahead vision, and it is important for tasks such as reading, driving, and recognizing faces. Diabetic macular edema, the buildup of fluid in this region, causes blurred vision and is the most common cause of vision loss in people with diabetic retinopathy. Three hree anti-VEGF drugs — Avastin, Lucentis, and Eylea — have all been shown to improve vision in people with diabetic macular edema.
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Risk factors
Having any kind of diabetes puts you at risk for diabetic retinopathy, and the longer you have diabetes, the greater your risk. Chronically elevated blood glucose, blood pressure, or blood cholesterol levels also increase the risk, according to the Mayo Clinic, as do pregnancy, tobacco use, or being Black, Hispanic, or Native American.
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Medical Jargon at a Glance
Aneurysm: A localized bulging of a blood vessel wall.
Angiogenesis: The development of new blood vessels.
Edema: Swelling caused by excess fluid trapped in the body’s tissues.
Proliferation: Rapid reproduction.
Retina: A layer in the back of the eye containing light-sensitive cells that send nerve impulses to the brain, which translates them into a visual image.
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Symptoms
In the early stages of diabetic retinopathy, there are usually no symptoms. Sometimes people notice vision changes, like trouble reading, that come and go. In the later stages, as blood vessels begin to leak blood into the vitreous, people may see dark, floating spots (sometimes called “floaters”) or streaks resembling cobwebs. Even if these visual changes go away, it is important to get treated right way to prevent scarring or more bleeding.
Screening
According to the American Diabetes Association’s (ADA’s) 2023 clinical practice recommendations, adults with type 1 diabetes should have an initial eye examination by an ophthalmologist or optometrist within five years of developing diabetes. Since people may have type 2 diabetes for years before it is diagnosed, the ADA recommends that people with type 2 have their initial eye examination at the time of diagnosis.
Children and adolescents who have had type 1 diabetes for three to five years should also be screened for retinopathy. Children and adolescents with type 2 diabetes should be screened as soon as possible after diagnosis.
Doctors check for retinopathy using a simple and painless dilated eye examination. The doctor applies eye drops to dilate (widen) the patient’s pupils in order to better visualize the retina and the optic nerve. Specifically, the doctor looks for any changes in blood vessels, such as leaking vessels or fatty deposits in the blood vessels, swelling of the macula, changes in the lens, or damage to nerve tissue.
Diagnosis
If the doctor suspects that diabetic retinopathy or macular edema is present, they may perform another test called fluorescein angiography to visualize damaged or leaky blood vessels in the retina. A fluorescein dye is injected into the bloodstream, typically through a vein in the arm. As the dye reaches the eye, this allows pictures to be taken of the retina’s blood vessels.
Treatment
Often, doctors begin treating retinopathy when it starts to progress to proliferative diabetic retinopathy (PDR) stage, or when diabetic macular edema occurs. For decades, PDR has been treated with panretinal laser surgery, which involves making 1,000 to 2,000 laser burns in the retina, which can shrink the abnormal blood vessels. Panretinal laser surgery, which sometimes requires more than one session, is most effective before these blood vessels have already started to bleed.
In roughly the past decade, another approach to treating diabetic retinopathy called anti-VEGF treatment has gradually moved to the mainstream for treating PDR. VEGF stands for vascular endothelial growth factor, a protein that promotes the growth and leakage of abnormal blood vessels in the eye. Blocking VEGF can reverse the growth of abnormal new blood vessels and decrease the amount of fluid in the retina. Anti-VEGF drugs include bevacizumab (brand name Avastin), ranibizumab (Lucentis), and aflibercept (Eylea). Most people with diabetic retinopathy require monthly injections for the first months of treatment, and less often after that. Lucentis and Eyelea are also approved for treating macular edema (see “What Is Diabetic Macula Edema?” for more information).
If there is severe bleeding into the vitreous gel, it is often treated with a surgical procedure called vitrectomy. Tiny ports or water-tight openings are placed in the eye, which allow the surgeon to insert and remove tiny instruments. Various instruments are used to remove the vitreous and conduct procedures such as eliminating scar tissue or repairing a detached retina. The vitreous is replaced with a clear salt solution or a bubble made of gas or oil, which is eventually replaced by the body with natural fluid. The procedure may be performed under local or general and is typically done on an outpatient basis.
Prevention
While there are several effective treatments available for treating existing diabetic retinopathy, it’s preferable to prevent it in the first place. Prevention of diabetic retinopathy begins with regular dilated eye exams at least once a year. Once it is detected, there are several different approaches to prevention. Lowering blood glucose levels has been proven to prevent or delay the development of retinopathy. Many large clinical studies, most notably the Diabetes Control and Complications Trial (DCCT), have shown that study participants with diabetes who keep their blood glucose levels as close to normal as possible are significantly less likely to develop retinopathy (and other complications) compared with those with less optimal blood glucose control. High blood pressure and high cholesterol levels also increase a person’s risk of diabetic retinopathy, so controlling blood pressure and cholesterol levels with lifestyle changes and medications can also help lower the risk of vision loss.
A bright future
The prognosis for diabetic retinopathy has been constantly improving. For example, one study reported in 2022 in the journal Diabetes Care demonstrated that the incidence (new cases) and prevalence (number of people with the condition) of visual loss from diabetic retinopathy in Finland have significantly decreased — despite the fact that the sheer number of people with diabetes has increased and the percentage of people who have it has increased over the same time period. The researchers attributed this decrease in visual loss to many factors, including the trend toward more intensive blood glucose control in the 1990s. Further, they pointed out that these findings underscore the importance of timely screening, diagnosis, and treatment of diabetes and diabetic retinopathy.
So, keep an eye on your sight! The steps you take today can help protect and preserve your vision for years to come.
Want to learn more about keeping your eyes healthy with diabetes? Read “What Is a Dilated Eye Exam?,” “Diabetic Eye Exams: What to Know,” “Eating for Better Vision and Healthy Eyes,” and “Keeping Your Eyes Healthy.”
