As an ophthalmologist, David Ingvoldstad sees much more about his patients' health than just their eyes. Thanks to the clues the eyes provide, he regularly alerts patients to possible autoimmune diseases like rheumatoid arthritis and lupus, monitors progression of their diabetes and once even suspected—correctly, as it turned out—that a patient had a brain tumor on the basis of the pattern of her vision changes.
Because the body's systems are interconnected, changes in the eye can reflect those in the vascular, nervous and immune system, among others. And because the eyes are see-through in a way other organs aren't, they offer a unique glimpse into the body. Blood vessels, nerves and tissue can all be viewed directly through the eye with specialized equipment.
With regular monitoring, eye doctors can be the first to spot certain medical conditions and can usher patients for further evaluation, potentially leading to earlier diagnosis and treatment. Clots in the tiny blood vessels of the retina can signal a risk for stroke, for example, and thickened blood-vessel walls along with narrowing of the vessels can signal high blood pressure. In some cases, examining the eye can help confirm some of the diagnoses or help differentiate disorders from each other.
"There's no question the eye has always been the window to the body," says Emily Chew, deputy director of the epidemiology division at the National Eye Institute. She adds, "Anybody with any visual changes…should be seeing someone right away."
Scientists are working to advance their knowledge of what the eye can reveal about diseases. For instance, researchers are studying how dark spots on the back of the eye known as CHRPE, or congenital hypertrophy of the retinal pigment epithelium, are associated with certain forms of colon cancer, and how dementia-related changes are signaled in the eye, such as how the eye reacts to light. Other scientists, like Chew, are studying how to keep the eye healthier for longer, which could be good for the health of the eye as well as the rest of the body.
The eyes can help predict stroke risk, particularly important to people with heart disease and other stroke risk factors. That is because blood clots in the arteries of the neck and head that might lead to stroke are often visible as retinal emboli, or clots, in the tiny blood vessels of the eye, according to the National Eye Institute.
The immune system's interaction with the eyes can be telling, too, yielding information about autoimmune diseases or infections in the rest of the body. Sometimes eye symptoms may appear before others, like joint pain, in patients.
For instance, inflammation in the optic nerve can signal problems in an otherwise healthy, young person. Along with decreased vision and sometimes pain, it can suggest multiple sclerosis. If the optic disc, a portion of the optic nerve, is swollen, and the patient has symmetrical decreased field of vision, such as a decreased right visual field in both eyes, they may need an evaluation for a brain tumor—a rare circumstance.