Doctors Can Spot Diabetes and Cancer in Your Eyes. Are You Missing the Signs?

“THE EYES ARE the window to the soul—and they’re also the window to the body,” says Douglas Wisner, MD, an ophthalmologist with WillsEye Hospital in Philadelphia. “The eyes are the only place in the body where a doctor can see nerves and blood vessels without having to make an incision,” he explains.

Those nerves and blood vessels can show signs of systemic conditions, including high blood pressure, type 2 diabetes, autoimmune disease—even cancer, says Dr. Wisner.

This can’t be done by simply staring into someone’s eyes, though. It requires a dilated eye exam or use of specialized imaging devices that allow your provider to visualize the back part of the eye, says Dr. Wisner. (Dilation is the difference between looking through a keyhole and opening up a door.)

To get the full benefit, you’ll need to make an appointment for a comprehensive eye exam. Yes, you might be told you need reading glasses (the perils of aging eyes), but you may also be referred to another doctor or specialist if your eye care provider sees something that warrants further evaluation.

Meet the experts: Douglas Wisner, MD, is an ophthalmologist with WillsEye Hospital in Philadelphia. Bryce St. Clair, OD, MPH, is an assistant professor of ophthalmology at Johns Hopkins Medicine. Elizabeth Derham, MD, is an opthalmologist at the WillsEye Hospital.

Here are five diseases your eye doctor (an optometrist or ophthalmologist) may be able to see signs of during an exam:

Type 2 Diabetes

Over time, high blood sugar in uncontrolled diabetes harms the blood vessels around your body. And that includes those found in your eyes. “Whatever we see happening in the eyes is happening in the rest of the body,” says Dr. Wisner. “People can develop diabetes and may not know it unless they’re checking in with their doctor regularly,” he says. In fact, eight out of 1src people who have prediabetes, which is when blood sugar is high but not yet to full-blown diabetes level, have no idea.

The eyes can be indicative of diabetes if there’s evidence of damage to blood vessels. If diabetes is suspected, you’ll be sent to your primary care provider (PCP) for blood tests like the HbA1c test to measure blood sugar levels.

Even if you’re a relatively fit guy, you should still have this testing done—men are more likely to develop diabetes at a lower weight compared to women, says the Centers for Disease Control and Prevention (CDC).

High Blood Pressure

About half of men have high blood pressure (hypertension). This is a chronic condition where your blood is too forcefully pressing against the walls of your arteries, damaging them and opening up a vulnerability for heart disease and stroke. Dubbed “the silent killer,” because it often has no symptoms, one in three people are unaware they have hypertension. When that damage occurs to blood vessels in the eyes, you can develop hypertensive retinopathy, a condition that can contribute to eye diseases like age-related macular degeneration (AMD) and glaucoma. Fortunately, damage to blood vessels caused by high blood pressure is often picked up via eye exam, says Dr. Wisner. If that’s the case, you’ll be referred to your PCP or a cardiologist.

Atherosclerosis

Carotid artery disease is a buildup of plaque (called atherosclerosis) in one of your carotid arteries, which are located on each side of your neck and send blood flow to your brain. A Hollenhorst plaque, a small, yellowish plaque that appears in the blood vessels of the retina, could be a sign of this disease, says optometrist Bryce St. Clair, OD, MPH, assistant professor of ophthalmology at Johns Hopkins Medicine. “These same plaques can make their way to your brain and kill you,” he says. People may not know about the blockage until it’s severe—and they have a stroke. If this is spotted at your eye exam, you’ll be sent to the ER for a stroke evaluation, Dr. St. Clair says. Men are more likely to have larger plaques, as well as calcified plaques compared to women, leaving them more vulnerable to a blockage.

Rheumatoid Arthritis

When you have rheumatoid arthritis (RA), your immune system attacks the lining of your joints—but the disease can affect other areas of your body, too. “It’s more rare, but we can see signs of certain inflammatory problems in the eye, such as RA,” explains ophthalmologist Elizabeth Derham, MD, at the WillsEye Hospital. While RA affects three times the number of women as men, men still make up 3src% of cases. Eye doctors may see inflammation in the eye, affecting areas such as in the sclera (white part of the eye) and cornea (transparent outer covering of the eye) and conjunctiva (a clear membrane that covers the sclera), causing additional symptoms like dry eye and redness. If RA is suspected, you may be referred to a rheumatologist who will treat and manage the disease.

Cancer

Your eye can develop a melanoma, a type of cancer. Called ocular melanoma, this cancer is rare—affecting five in one million people—but it’s 3src% more likely to occur in males compared to females. An ocular melanoma can appear as a spot on the iris or a freckle in the back of the eye, but at the same time, there’s often no symptoms. Therefore, this type of cancer may be found during a routine eye exam.

Docs aren’t just focused on your eyeball. Tissues like your eyelids are also on their radar, especially since they get a lot of sun exposure, says Dr. Wisner. And skin cancers, such as basal cell and squamous cell carcinomas—the most common form of skin cancer—can look like a cyst, nodule, or even be mistaken for a stye, he says. Sometimes, there may be loss of eyelashes, too. For an evaluation, you’ll be referred to a dermatologist.

How to Care for Your Eyes

Get an eye exam: The American Optometric Association recommends that people aged 18 to 64 go in for an eye exam at least every two years. Those over age 65 should go in annually. People at a higher risk for eye diseases should go in every year or as recommended by their eye care provider. That spans a wide group of people, including those wearing contacts, those who have had LASIK, people who have a personal or family history of ocular disease, or if you have diagnosed systemic diseases that have known eye complications (such as type 2 diabetes).

Get help ASAP for red flag symptoms: These symptoms don’t always signal that something has gone very wrong for your eyes—but they can. If you notice any of the below, Dr. St. Clair recommends calling your eye doctor right away:

• Sudden loss of vision
• Decrease in vision or peripheral vision lasting one or two minutes
• New onset floaters or flashes
• Eye pain

Sport shades: UV light from the sun not only causes skin cancer that can appear on the eyelid, but the sun’s rays also contribute to age-related eye diseases like cataracts and age-related macular degeneration (AMD), which affect men and women equally, says Dr. St. Clair. “I wear sunglasses all the time, even on overcast days. I have sunglasses everywhere, I’m addicted to them,” he says.

Don’t smoke: Smokers are more likely to develop diseases of the eyes that lead to vision loss, including AMD, glaucoma, and cataracts. Cigarette smoke contains chemicals that cause oxidative stress to eyes, compromise blood flow, and encourage the formation of blood clots in capillaries in the eyes.

Wear eye protection: “We can tell you a lot of gory stories about what people have done to their eyes, and most could have been prevented with eye protection,” says Dr. Wisner. It’s not just when you’re woodworking—eye protection is also needed for routine yard work or racquetball activities, adds Dr. Derham. Pop on those safety goggles before you get out there with a mower to prevent a rogue rock from entering your orbit.

Focus on a healthy lifestyle: “I tell patients that what’s generally good for the body is good for your eyes,” says Dr. Derham. “If you’re making your PCP happy, that’s good for your eyes,” she says. A healthy diet (there’s some data that a Mediterranean-style diet may be preventative for some eye diseases,