En español | The benefits of annual appointments with your ophthalmologist go well beyond keeping your eyes in working order: A close inspection of the lens, retina and optic nerve can reveal a host of systemic disorders — high blood pressure and diabetes among them — sometimes before other symptoms become evident.
"An eye exam is one of the few exams where, without doing blood tests, invasive imaging or surgery, we can actually look inside the body,” says Brian Stagg, M.D., an ophthalmologist and retina specialist at the University of Utah's John A. Moran Eye Center. “I can see blood vessels and nerve tissue that actually runs all the way to the brain.”
Here, some health conditions doctors can discover:
1. High blood pressure
“Most bleeding in the eye is harmless, sometimes caused by coughing or sneezing too hard,” says Dimitra Skondra, M.D., associate professor of ophthalmology and visual science at the University of Chicago. “But it can also be associated with high blood pressure.” That might present itself as a tiny blood vessel that breaks in the white of the eye and leaks blood (a subconjunctival hemorrhage).
Another sign of underlying hypertension, says Skondra, is “a little bit of swelling” in the eye. When someone has high blood pressure over a long period of time, the arteries of the retina may stiffen, and cause bulging in the eye when pressed against a blood vessel (something called arteriovenous nicking).
2. Heart disease
Because the health of your eye is connected to the health of your heart, eye exams can detect a number of cardiovascular conditions, including clogged arteries, often before the patient even knows there's a problem. “Sometimes we can see little plaque deposits inside the eye that have broken away from buildup on the carotid artery, which supplies most of the blood supply to the brain,” Stagg says. They can cause a stroke if they reach the brain. If you do have signs of plaques, an ophthalmologist will order imaging or send you to your primary care doctor.
And, while diagnostic methods are still being studied, your eyes can also display evidence of ischemia — decreased blood flow due to heart disease. “The human retina doesn't regenerate, so when there's interruption of blood flow, [cells in] the retina die,” says Mathieu Bakhoum, M.D., a retina surgeon at UC San Diego Health. He's lead author of a study, conducted by the Shiley Eye Institute at UC San Diego Health, in which researchers identified a potential marker for the presence of cardiovascular disease. “When cells die,” Bakhoum explains, “they leave behind visible damage, a kind of a permanent mark, which we call retinal ischemic perivascular lesions, or RIPLs.” When researchers counted the lesions on optical coherence tomography (OCT) scans (a noninvasive diagnostic tool used to create images of the retina), they discovered that people with cardiovascular disease had more of these lesions. Bakhoum says more research could lead to RIPLs becoming a useful marker for identifying cardiovascular disease, before a heart attack or a stroke occurs.
This disease is sneaky. “Patients may show no symptoms and have perfect vision, and an eye doctor will find signs indicating underlying diabetes,” says Skondra. In fact, in 2017, optometrists discovered more than 400,000 cases of diabetic retinopathy in patients who hadn't even been diagnosed with diabetes. Retinal imaging devices can help doctors get a good look inside the eye to catch retina damage in its early stages and prevent vision loss. “There's a perception that when diabetes starts to affect your eye, you're going to go blind,” Stagg says. “But when it's caught in time, there's a lot we can do to prevent that to save your vision."
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As with heart disease, diabetes targets the blood vessels in the retina. Early on, eye doctors can detect microaneurysms, dilated capillaries, and swollen blood vessels, which block blood flow. In the advanced stage of diabetic retinopathy, new blood vessels start to grow in the retina, but they're abnormally shaped and weak, which means they can leak blood into the eye, in front of the retina. This can lead to vision loss.
Another tell-tale sign of diabetes: the appearance of cotton wool spots, which appear as fluffy white patches on the retina. They usually disappear without treatment but can be an indication of the disease.
4. Rheumatoid arthritis
This chronic inflammatory disease, which affects the joints, can target the eyes as well. Dry eye is the most common eye symptom of rheumatoid arthritis. Another way rheumatoid arthritis can affect the eye is through inflammation, particularly inflammation of the sclera (the thin white outer layer of the eye), says Stagg. The reason: Inflammatory conditions affect collagen, the main component of connective tissue, and the sclera is composed mostly of collagen.
5. Thyroid disorder
Protruding eyeballs and retracting lids (that's when the upper or lower eyelid margins are drawn back from the normal position) are signs of an overactive thyroid gland, or hyperthyroidism. “It sometimes appears with dry eye, because the lids can't cover the surface of the eye as well,” says Angela Elam, a clinical assistant professor in ophthalmology and visual sciences at the University of Michigan. An eye doctor can use an exophthalmometer to measure how far the eyeball protrudes.
6. Parkinson's disease
Currently, there is no conclusive test doctors can use to identify Parkinson's disease. The diagnosis is based on symptoms and a neurological and physical exam. Not surprisingly, it's misdiagnosed up to 30 percent of the time, according to the Cleveland Clinic. That may change. RightEye, which received FDA clearance in 2018, tracks eye movement measurements (as a patient stares at a screen and follows prompts) to help evaluate for Parkinson's. Studies have shown that people who suffer from Parkinson's disease generally have ocular tremors, usually in the very early stages before other symptoms are noted. By using eye-tracking technology to identify ocular tremors, the RightEye Vision System can help to diagnose Parkinson's for earlier intervention.
“The eyelid is one of the most common places to get skin cancer from sun exposure,” says Elam. The lower lid is the most likely spot. More rarely, melanoma can be detected inside the eye --— for example, near the iris or the muscle fibers that surround the lens — where it can be seen with a microscope.