Diabetic Retinopathy: How Can I Tell if Diabetes is Affecting My Eyes?

Two ophthalmologists from the acclaimed Willis Eye Hospital tell you what you need to know about diabetic retinopathy which can lead to vision loss.

purple light on man's face with hand holding wire High blood sugars over an extended period of time can lead to vision loss through a condition known as diabetic retinopathy. (Photo: Pexels, David Cassolato)

Diabetic retinopathy is the most common complication of diabetes and a leading cause of blindness in working age American adults. 1,2

From 2010 to 2050 the number of Americans with diabetic retinopathy is expected to nearly double, from 7.7 million to 14.6 million. 3

The longer a person has uncontrolled diabetes, the greater chance for the eye disease.

“People with diabetes who have poor control of their disease with higher sugars and hemoglobin A1c’s that are running above the 8 or 9 plus range, have a higher risk of the disease,” says Jason Hsu, MD, a retina surgeon at Wills Eye Hospital in Philadelphia. “In addition, hypertension accelerates the damage we see in the eyes. Some people will rapidly lose vision if both factors are out of control.”

What is Diabetic Retinopathy?

In diabetic retinopathy, high blood glucose levels damage the linings of the blood vessels located at the back of the eye, causing them to leak and bleed into the retina.

This robs the retina—the light sensitive layer of tissue located at the back of the eye—of oxygen and nutrients. 

“Blood vessels are basically piping, and when pipes become damaged, they can leak,” says Sunir Garg, MD, a retinal surgeon and clinical spokesperson for the American Academy of Ophthalmology. “When blood vessels in the eye become damaged from diabetes, they can leak blood and plasma, which can damage the retina.”

As the disease progresses, abnormal blood vessels can grow in the wrong places in the eye. These fragile vessels can also leak or, in some cases, burst, filling the vitreous of the eye with water and blood and leaving the patient with a sudden loss of vision. The vitreous is the clear gel that fills the space between the retina and lens of the eyeball.

Diabetic Retinopathy: A Progressive Loss of Vision

Diabetic retinopathy is a progressive disease, which can start as asymptomatic.
In nonproliferative or background diabetic neuropathy, the early phase of the disease, blood vessels in the retina deteriorate so that fluids, fats and proteins leak from the damaged blood vessels. These fluids can collect in the retina, causing blurred vision and injuring the sensitive tissue.

“When fluid affects the central vision of the eye, it’s called diabetic macular edema, which can be treated with lasers or more typically with medicine injections,” says Dr. Garg. The macula, located in the center of the retina, is responsible for sharp, clear, straight ahead vision.

Over time, however, retinal blood vessels can become so damaged that they no longer carry oxygen or nutrients to the retina. This is called macular ischemia. Blood can no longer reach the macular tissue, causing a loss of vision.

Proliferative diabetic neuropathy occurs in later stages of the disease, when new, abnormal and unstable blood vessels begin to grow on the surface of the retina. Bleeding from these leaky vessels can lead to local irritation and scarring. If the bleeding seeps into the vitreous—the clear gel between the lens and the retina—it can cause floaters or, if the bleeding is excessive, block vision.

Scar tissue from these abnormal vessels can also create a retinal detachment, a very serious problem that can affect both central and peripheral vision. 4

“Rather than being helpful, these new blood vessels can burst open and create scar tissue which can pull on the retina and cause a retinal detachment,” says Dr. Garg. “Fortunately, before that occurs, we can fix the bleeding into the eye and the scar tissue with medicine injections into the eye, a type of laser called panretinal laser photocoagulation and sometimes, surgery.”

Diagnosis and Symptoms

Diabetic retinopathy can be diagnosed with a dilated eye exam performed by an ophthalmologist. In addition, tests such as a fluorescein angiogram and ocular coherence tomography (OCT) can be conducted. The angiogram test involves the injection of a contrast agent or dye into your arm.

When to go for a first retinal exam depends on whether you have type 1 or type 2 diabetes, says Dr. Hsu. Since it’s rare to find diabetic retinopathy in a newly diagnosed type 1 patient, he suggests scheduling a retinal exam within five years of diagnosis.

A Different Story for Type 2s

“Type 2 patients often have smoldering undiagnosed sugars for a long time before they are actually diagnosed and should have an immediate retinal eye exam upon diagnosis,” he explains.

Although diabetic retinopathy can be asymptomatic, there are noticeable symptoms in later stages of the condition. These include an increase in the number of floaters in the eye, blurred vision, changes from blurry to clear vision, blank or dark areas in the field of vision, poor night vision and perceiving colors as faded or washed out. Symptoms usually affect both eyes. 5

What Is the Best Treatment for Diabetic Retinopathy?

In mild cases of diabetic retinopathy treatment may not be necessary. Patients should watch their blood sugars, cholesterol levels, and blood pressure, maintain a healthy weight, exercise, quit smoking, and see their eye doctor on a regular schedule. 

Early treatment is essential in preventing vision loss from more advanced diabetic retinopathy.

In most cases, the condition can be treated effectively. The “gold standard” of current treatment are injections of anti-VEGF (Vascular Endothelial Growth Factor)6 into the eye, to prevent new vessel growth and swelling under the macular area of the retina, and perhaps to improve vision loss.

While these injections need to be repeated frequently during the first year of treatment, they typically drop off over time. Anti-VEGF medications include Avastin, Lucentis and Eylea.

Corticosteroids are considered a second-line treatment for cases that do not respond well to anti-VEGF medications.

“One downside to steroids is that they can cause a higher eye pressure which can lead to glaucoma, a disease that affects a nerve in the back of the eye that can cause vision loss,” says Dr. Hsu.

Laser surgery can sometimes help seal off leaking blood vessels and reduce pressure in the macula. Lasers can also be employed to shrink blood vessels and stop them from re-growing. But they also carry risks.

“If the damage is in the center of the retina, we can’t use lasers since they can leave a burn that can also cause a loss of vision,” says Dr. Hsu.

Some cases—such as retinal detachment—may require 30 to 90-minute surgeries, which can help protect against further vision loss and can improve vision in a number of cases.

What You Can Do to Prevent Vision Loss

Controlling your sugars, cholesterol and blood pressure, maintaining a healthy weight, quitting smoking and getting exercise can improve early background diabetic retinopathy, and even, in some cases, bring some vision back.

“Good sugar and blood pressure control from the time a person is diagnosed with diabetes is critical,” says Dr. Garg. “If patients can optimize their blood sugar, blood pressure and cholesterol control, they may never need treatments from us and if they do need treatments, they usually respond better.”

Dr. Hsu agrees. “For some people who are getting injections their high blood pressure and high sugars can still cause damage.”

“We also know that even patients who previously had poor sugar and blood pressure control will benefit from improving them even years after the initial diagnosis,” says Dr. Garg

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