WHAT CAN MY BLINKING TELL ME ABOUT MY HEALTH?

Q I feel like I'm blinking more often than usual.

What can blinking tell me about my health? And why do we blink?

A We blink about once every three to five seconds and usually unconsciously, despite losing an incredible amount of our daily visual input to blinking — up to 10 per cent.

Blinking serves several practical purposes: It wets and cleans the surface of the cornea and can reflexively protect the eye from rapidly approaching objects.

A change in blinking might herald a health problem. Here are some reasons blinking may change that can tell you something about your health:

Slow or infrequent blinking: Decreased blinking can be an early sign of Parkinson's disease. One important neurotransmitter influencing our ability to pay attention and show flexibility is dopamine. Several studies suggest the rate at which we spontaneously blink mirrors the neurotransmitter's activity in our brains — the lower the dopamine, the more we fixate on one subject, and the less we blink.

Patients with Graves' disease also experience changes to their blinking pattern, which may be related to cornea damage. Other neurological conditions, such as stroke, can slow the normal blinking rate. Slower blinking has also been associated with head injury among athletes.

Excessive blinking: Increased blinking can be a sign of sleepiness while trying to perform a demanding task such as driving while drowsy (in which case, stop and rest). Pain or very bright lights can cause more frequent blinking. Or your body may be compensating for dry eye disease, which occurs for a number of reasons, including Sjogren's syndrome or side-effects from medications like antihistamines.

Dry eye disease is common among frequent screen-users. We blink less frequently when we stare at our screens.

Set 20-minute timers to step away for a minute or two from your screen. Try “blind working” — closing your eyes for deliberate breaks when you don't need to have them open, during a telephone call, for example. Heightened screen time may be associated with damage to glands that keep our eyes healthy, as well as myopia.

Why do we blink?

In many situations, people blink in unexpected patterns that don't seem to have anything to do with maintaining their eyes' moisture.

In the 1920s, scientists wondered: If blinking was not simply there to dust off the corneas, what did it really mean?

Some observations made intuitive sense — they noted people blink more frequently while smoking; smoke is a known corneal irritant. They also found people blinked less frequently while reading than while talking, when the environment was otherwise the same — and oddly, that people reading almost always blinked at punctuation marks instead of text.

Other findings were just as puzzling. Unexpected sounds, even if not loud, caused children to blink. And people blinked more frequently when they became angry or anxious.

Decades of research has revealed that blinking is much more than the windshield wiper of the body but rather a window into the state of our minds — how carefully our attention is focused and whether we're ready for new stimuli.

Studies have shown that increased spontaneous blinking can be a sign of gathering new information — especially when it challenges the “rules” of a known environment.

For instance, babies in bilingual households blink more rapidly as they switch between hearing different languages spoken, which correlates to signalling in areas of the brain governed by dopamine. And people blink in synchrony when watching the same movie — researchers have found that we tend to stare continuously while the action of the main character unfolds, but we all start to blink unconsciously during the same implicit narrative breaks — such as when there's a shot with no humans in the scene.

In a similar way, blinking plays a role in our social communication. Scientists have measured that when two people are communicating smoothly with each other and holding the other's interest, their blinking patterns start to align.

How did humans evolve to blink?

Scientists believe blinking developed several times across evolutionary history — and in some cases, like with snakes, became lost again. A study of mudskippers published last year in the Proceedings of the National Academy of Sciences hypothesized that it was the transition from aquatic life to land that made blinking beneficial to survival — even for our own ancestors, who also emerged from the sea several hundred million years ago.

One reason blinking on land is critical is because the corneas of our eyes don't have blood vessels and so they derive oxygen by diffusion from the environment surrounding them. Oxygen diffuses more easily across wet surfaces, and spontaneous blinking helps maintain a thin, fluid film layer on our eyes. Another reason is that dangerous objects travel much more quickly through thin air than they would through water — so blinking reflexively to shield the eyes from injury is significantly more important on land.

What I want my patients to know

People often buy laptop raisers or elevate their screens to eye level. Instead, try placing the screen at a 10-degree downward gaze angle (and ideally two to three feet away from you). Doing so may relax the muscles around your eye to help you blink more completely, and it can reduce tear evaporation.