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10 Diseases Eye Dilation Can Spot

Dilating your eyes can help your doctor diagnose serious problems such as diabetes, high blood pressure or a brain tumor


spinner image close up of a blue dilated eye during an eye exam
Christian Weber / Getty Images

Getting your eyes dilated is no fun. It distorts your close vision and makes bright light painful for several hours after your appointment.

But optometrists and ophthalmologists say the short-term inconvenience is worth it.

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The special drops that your eye doctor uses for dilation allow your doctor to see all the different parts of your eye and spot early signs of problems that could threaten your eyesight and your overall health. In fact, a dilated eye exam can detect more than 270 diseases and abnormalities, according to the American Optometry Association.

Looking into an undilated eye compared to one that’s been dilated is “like the difference between looking through peephole or opening up the door and seeing all the way into the room,” explains Ethan Greenberg, M.D., assistant professor at the University of Minnesota Medical School and an ophthalmologist with M Health Fairview.

Unfortunately, many Americans who should have annual dilated eye exams aren’t getting them. Fewer than 60 percent of the 93 million adults in the United States at high risk for vision loss received a dilated eye exam in the preceding year, according to a 2017 survey.  

Annual exams are especially important for older adults, who are at higher risk of developing eye problems such as cataracts, glaucoma and macular degeneration.

Is it really necessary to have your eyes dilated?

Some optometrists have started offering “no-dilation” exams. As an alternative to dilation, they use retinal imaging devices to look at the inside of the eye, which can sometimes cost the patient extra.

However, dilation is still the gold standard, Greenberg says.

“Nothing fully replaces a dilated exam,” he says. “You’re going to miss some things sometimes without a dilated exam.”

A 2017 study published in Seminars in Ophthalmology compared the use of Optomap, a common retinal imaging device, to a traditional dilated eye exam for evaluating patients with a history of retinal detachment. The device’s ability to detect retinal holes, tears and scarring was “poor” compared to a dilated eye exam, the study found.

The American Optometric Association’s evidence-based clinical practice guidelines note that dilation is required for a thorough evaluation of ocular structures. The organization recommends that patients ages 65 and older have an annual eye exam with dilation at least once a year.

What your doctor can catch with an eye exam

During a dilated eye exam, your doctor can check for many different diseases, including some that have no early warning signs.

Here are some of the diseases and conditions your doctor can spot with a dilated eye exam:

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1. Macular degeneration

This eye disease happens when aging causes damage to the part of the eye that controls sharp, straight-ahead vision, leading to vision loss and possibly blindness. Catching it early can allow for treatments that can slow its progress.

2. Glaucoma

Because glaucoma often has no symptoms, many people don’t know they have it until it causes significant, irreversible vision loss. Although there is no cure for glaucoma, if it’s caught early, there are treatments that can preserve treatments and prevent vision loss.

3. Cataracts

Dilating your eyes makes it easier for your doctor to check for early signs of cataracts, a slow clouding of the eye’s lens that makes it difficult to see, especially at night.

4. Diabetes

An eye exam can reveal damage to the blood vessels in the back of your eye, an early sign of diabetes. “We can see blood vessels in the retina better than anywhere else in the body,” Greenberg says. Diabetes is one of the leading causes of blindness in older adults.

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5. High cholesterol

If your doctor sees a white ring around the edge of your cornea, that can be a sign of high cholesterol, which increases your risk of heart disease and stroke, says Sharon Fekrat, a professor of ophthalmology and a retina specialist at the Duke University School of Medicine.  

Can You Drive After a Dilated Eye Exam?

Your eyes will likely stay dilated for four to eight hours, with your eyesight gradually improving over time. How blurry your vision will be and how long the blurriness lasts will depend on what type of drop your doctor uses and how your eyes react. While many doctors allow patients to drive with dilated eyes, your safest bet is to make arrangements to have someone take you home after your appointment.

6.  High blood pressure

A dilated eye exam can reveal uncontrolled high blood pressure, which increases your risk of heart attack and stroke. During an exam, “the very small blood vessels look narrowed in the retina, and instead of looking red, they are slightly pink or silvery,” Fekret says. “They are also much narrower than we would expect.”

7. Sexually transmitted diseases

Syphilis, herpes, chlamydia, HIV, gonorrhea, genital warts and pubic lice can all affect layers of the eye. Untreated syphilis that shows up in the eye can lead to vision loss and even blindness. Herpes that has been dormant in older adults can appear in the eye if your immune system weakens, Greenberg says.

8. A brain tumor

An undiagnosed tumor can cause pressure to build up in the brain and cause changes to your optic nerve that your doctor can see.

9. Cancer

A leukemia reoccurrence is sometimes diagnosed through an eye exam, because leukemia cells tend to collect in the eye, Fekrat says. Breast cancer, prostate cancer and lung cancer can also affect layers of the eye.

10. Infections and inflammation

Bacterial infections sometimes show up in the eye as blood spots on the retina, especially if it’s an infection like acute endocarditis that affects the heart and blood vessels, Greenberg says. Rheumatoid arthritis and other inflammatory conditions can also affect the eye.

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