The Unique Eye Trait Only 50% Of People Have

If you have the power to unfocus your eyes on command, you may not even realize you're experiencing something only 50% of people can, and if you're in the other half of the population, the very idea of voluntarily making your vision go blurry might sound flat-out bizarre. It's one of those quirks, like the ability to wiggle one's ears, that doesn't really factor into our day-to-day survival, yet it's an interesting factoid nonetheless, and one that can actually help us better understand how the human eye works in general.

The power of vision is created when light passes through the eye, entering the aperture of the pupil before being focused through the lens and onto the retina. The lens of the eye is held in place by a ring of muscle fibers known as the ciliary muscles, which expand and contract to focus light through and onto the retina. When the ciliary muscles are contracted, they pull the lens tight, which focuses light onto the retina more precisely. When the ciliary muscles are relaxed, the lens of the eye flattens out, focusing light less precisely, and making the vision blurry.

The ability to intentionally relax the ciliary muscles is known as negative accommodation, or an intentional divergent squint, and people with this ability can unfocus their vision at will. You can tell if another person is doing it because their eyes drift slightly apart, like the opposite of crossed eyes. The real question is, what's the point of this ability?

There is no practical necessity for an intentional divergent squint, but some people with the ability find that it can have a helpful purpose. It should come as no surprise the eyes play a part in mental focus, and the act of intentionally blurring one's vision can feel like a manual override switch that literally refocuses the mind. Some visual artists who are able to control their ciliary muscles will do so in order to literally get a new perspective on their creative work. An intentional divergent squint can also make peripheral objects clearer while what is directly in front of the viewer goes blurry.

Unfortunately for people with this ability, repeatedly unfocusing and refocusing your vision can lead to problems. An intentional divergent squint prevents the eye from doing what it is built to do, and puts unnatural strain on the ciliary muscles. Excessively doing this over a long period of time can weaken the eyes' ability to focus, leading to blurry vision even when it's not on purpose.

While the ability to control your ciliary muscles is present in about half the population, a smaller group of people experience something called accommodative dysfunction, where their eyes unfocus involuntarily. This can happen when the ciliary muscles cannot sustain contraction or spasm. Corrective lenses may help such an issue, which could otherwise lead to long-term issues with eye fatigue and blurred vision, the same risk faced by people who can voluntarily unfocus their eyes.