What the eyes say about our health

Scientists at the University of California, San Diego have developed a smartphone app that can detect early signs of Alzheimer’s disease and other neurological conditions. The app uses the phone’s infrared camera to track changes in the size of a person’s pupils at a sub-millimeter level. These measurements can be used to assess the person’s cognitive status.

As technology evolves, the eyes will become increasingly useful in diagnosing all kinds of diseases and conditions because, being transparent, they require much less invasive examination methods than other parts of the body.

But even without technology, it’s possible to spot a number of health problems just by looking at your eyes. These are some of the warning signs:

pupil size

The pupil responds instantly to light, getting smaller in bright environments and larger in dim conditions. Slow or delayed responses in pupil size can point to various diseases that can include serious conditions such as Alzheimer’s disease, as well as the effects of medication use and evidence of drug use.

Dilated pupils are common in those who use stimulant drugs such as cocaine and amphetamine. Very small pupils can be seen in heroin users.

red or yellow eyes

A change in the color of the sclera (the “whites of the eyes”) suggests that something is wrong. Behind a red, bloodshot eye there may be an excess of alcohol or drugs. It can also be due to an irritation or infection that, in most cases, goes away in a few days.

If the color change is persistent, it may be a sign of a more serious infection, inflammation, or a reaction to the contact lenses or their fluids. In extreme cases, redness indicates glaucoma, a disease that can lead to blindness.

If the sclera turns yellow, this is an obvious sign of jaundice and a diseased liver. The underlying causes of jaundice are very varied. These include inflammation of the liver (hepatitis), genetic or autoimmune conditions, and certain medications, viruses, or tumors.

Yellow sclera is a possible sign of liver disease.

Red stain

A blood-red spot on the white of the eye (subconjunctival hemorrhage) can look frightening and is always the result of a small, localized blood vessel bursting.

Most of the time the cause is unknown and it goes away in a few days. However, it can also be an indicator of high blood pressure, diabetes, and blood clotting disorders that cause excessive bleeding. Blood-thinning medications, such as aspirin, can also be the cause, and if the problem is frequent, it might be suggested that the dose be reviewed.

Man with a blood stain on his eye
An eye bleed is rarely as serious as it seems.
YewLoon Lam/Shutterstock

Ring around the cornea

A white or gray ring around the cornea is often linked to high cholesterol and an increased risk of heart disease. It can also reveal alcoholism and is sometimes seen in the eyes of older people, giving it the medical name arcus senilis.

An eye with arcus senilis.
Arcus senilis is common in older people.

fat lump

Sometimes the most alarming features that can appear in the eyes are actually the most benign and easy to treat. A yellowish fatty lump on the white of the eye is a pinguecula, a small deposit of fat and protein. It is easily remedied with eye drops or with a simple operation.

A pterygium, which appears as a pinkish growth on the white part of the eye, is not a sight hazard until it begins to grow on the cornea (the colored part of the eye).

Fortunately, pterygium grow very slowly. Like the pinguecula, it can be easily removed. In fact, it must be removed long before it reaches the cornea.

If allowed to continue to grow, the pterygium will form an opaque “film” on the cornea, obstructing vision. One of the main causative factors for both pinguecula and pterygium is believed to be chronic exposure to ultraviolet light from the sun.

An eye with a pinguecula
A pinguecula is a yellowish growth on the conjunctiva.

Bulging eyes

Googly eyes can be part of a normal facial feature. But when previously non-bulging eyes begin to bulge forward, the most obvious cause is a problem with the thyroid gland, and it needs medical attention. A single bulging eye can be caused by an injury, infection, or, more rarely, a tumor behind the eye.

Person with bulging eyes.
Bulging eyes can be a sign of a thyroid problem, such as Graves’ disease.
Jonathan Trobe/Wikimedia Commons, CC BY

Swollen or twitching eyelids

The eyelids can also indicate many diseases. Most of them are related to minor conditions of the glands of the eyelids. A common condition is the stye or chalazion. It appears as a red lump on the upper and, less commonly, the lower eyelid and is caused by a clogged sebaceous gland. The stye usually goes away on its own or with warm compresses. If it persists, it must be removed with a simple procedure.

A twitching eyelid (ocular myokymia) can be an irritation, even an embarrassment, and is often perceived as much more than it is. In most cases, it’s perfectly harmless and related to stress, nutrient imbalance, or consuming too much caffeine.

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