Why a dilated eye exam is important for diabetics

People with diabetes need to pay special attention to many things, including their blood sugar levels, what they eat, and, yes, their eyes. 

Here’s why: Diabetes may cause an eye condition called diabetic retinopathy. Left unchecked, this disease may cause serious vision loss. In fact, it’s the leading cause of blindness in American adults, according to the National Institutes of Health.¹

Diabetic retinopathy might not cause any symptoms in its early stages, so people may not know they have it. An eye care provider may detect it during a routine exam, which is why regular eye exams are important.

Read on to find out exactly what diabetic retinopathy is, why it’s important for an eye care provider to detect it early, and how it may be diagnosed.

Diabetic retinopathy affects the blood vessels in the retina, the light-sensitive layer of tissue located at in the back of the eye. It’s caused by the high blood sugar (or glucose) levels that can be common in people with diabetes.²

Over time, high blood sugar levels could damage the tiny blood vessels in the body, including those in the retina. Those increased glucose levels may cause the tiny veins in the retina to:²

• Bleed 
• Leak fluid
• Swell

This could block the flow of blood and oxygen to the eye and may cause blurry or cloudy vision.

When it becomes more advanced, new blood vessels can grow in the retina, explains Ryan Bulson, O.D., an optometrist and professor of optometry at the Pacific University College of Optometry in Forest Grove, Oregon.

Eventually, all those new blood vessels may lead to retinal detachment. That’s when the retina is pulled away from the normal position in the back of the eye. It may trigger vision loss too. 

“The worst-case scenario to not detecting and treating diabetic retinopathy early is it can cause you to lose your vision,” says Dr. Bulson. 

The longer someone has diabetes, the higher their risk of developing diabetic retinopathy, according to the National Eye Institute. Over time, more than half of people with diabetes will develop the eye condition.²

The Centers for Disease Control and Prevention estimates that 9.6 million people in the United States have diabetic retinopathy. Among adults with diabetes, the highest rates are among those ages 65 to 79.³

In the early stages, people may not have symptoms, but symptoms may show up as this eye disease gets worse. These signs include:^1,4

• Blurry vision 
• Difficulty seeing well at night  
• Distorted vision or changes in vision 
• Seeing spots or floaters 
• Trouble seeing colors 

Anyone with diabetes who has any of these symptoms shouldn’t wait for their yearly eye exam to see their eye care provider. The sooner diabetic retinopathy is identified, the better the chances of protecting the person’s eyesight. 

During a standard eye exam, the eye care provider will test vision and eye health in several ways by having the patient:⁵

• Read letters on an eye chart to determine sharpness of eyesight 
• Have them look in different directions to check eye muscles 
• Measure eye pressure to check for glaucoma
• Examine the pupils to make sure they get smaller when exposed to bright light 

Another key test is when the eye care provider uses eye drops to dilate (or widen) the pupils. That allows eye care providers to have a better view of the back of the eye, including the retina. 

Once the pupils are dilated, the eye care provider may see signs of diabetic retinopathy. “The pupil is our window to view the retina, so a dilated pupil gives us a much larger window through which we can see any potential damage to the retina,” says Dr. Bulson.  

An eye care provider may check for a few things. “We may see microscopic bleeding that shows up in little red spots on top of the retinal tissue,” he says. Another way: If the blood vessels are leaking lipid material or fat, which can show up as yellow in the retina, he adds.

Another thing a doctor may find is cotton wool spots, which are little white feathery lesions on the retina, Dr. Bulson explains. (Lesions are areas of damage.) “These lesions tell us the retina is being starved of oxygen, and this ups the level of severity,” he says.

If an eye care provider sees these signs of diabetic retinopathy through dilated pupils, they may order additional tests. One of these is called a fluorescein angiogram. It lets eye care providers get a more detailed view of the blood vessels in the eye.²

When people get a diagnosis of diabetic retinopathy, their treatment depends on the severity of the disease. 

There isn’t necessarily a treatment for the early stages of diabetic retinopathy, notes Dr. Bulson. “It’s really about the patient making lifestyle changes to better manage their diabetes. This includes being mindful of what they’re eating, getting regular physical activity, taking prescribed medications, and keeping regular appointments with the providers managing their diabetes,” he says.

Other potential treatments include injections in the eye, laser procedures or eye surgery. In this case, the eye care provider will refer the patient to an ophthalmologist, a medical eye care provider with advanced training, to perform eye surgery.²

Dr. Bulson also says that an eye care provider may reach out to the patient’s primary care provider or other health care providers to inform them about their diabetic retinopathy diagnosis. “This is so all providers are collaborating to ensure the best health outcomes for the patient,” he explains. 

It’s a good idea for everyone to get their eyes checked by an eye care provider regularly, but it’s especially important for people with diabetes to get an eye exam every year, notes Dr. Bulson.

An eye care provider may also be the first person to diagnose someone just by taking a close look at the retina. “In the early stages of diabetes, about 40% of people don’t even know they have it,” says Dr. Bulson.

The good news is that diabetic retinopathy could be reversible in the early stages, reports Dr. Bulson. “I’ve seen early signs in patients, and they come back 6 months later and the signs aren’t there anymore because they’re eating better and exercising,” he says. “You’re not on a one-way track if you’re in the early stages. You have control.”

An eye care provider may also want to schedule visits more often after a person has gotten a diagnosis. “We may want to see the patient as often as every 3 to 6 months to stay on top of it and monitor any changes,” says Dr. Bulson.

The bottom line: Diabetic retinopathy may be preventable. The key may be to keep blood sugar levels in check and to schedule regular appointments with an eye care provider, as well as with a diabetes care team.