Researchers have found that we all perform a new, distinct eye movement on a daily basis. The catch is that we don't actually notice that we do it. The new movement is hidden by our blinking, but it works to "reset" our eyes to stabilise the images that we perceive.
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"We were really surprised to discover this new type of eye movement and it was not what we had anticipated from the experiment," says one of the team, Mohammad Khazali from the University of Tübingen in Germany. "We had expected to find that another, already well-known type of eye movement is synchronised to blinking."
Khazali and team weren't actually looking for a new movement at all. Instead, they were studying torsional optokinetic nystagmus (tOKN), something that happens when we blink. This occurs when you are looking at a rotating object, and it makes the eye able to sense the motion.
When you are looking at something that rotates, your eyes focus on a singular spot and then snap to the opposite side to keep track of the movement - that is tOKN. The team looked at eleven subjects to see how their eyes moved when they followed a track of dots.
They had assumed, based on what they already knew, that the tOKN would reset the eye's movement to avoid muscle strain. Instead, these blinks were imperfect and caused deviations of 3 to 8 degrees, depending on the person. This pushed the muscles to their max.
"The eye's sharpest vision is enabled by a spot on the light-sensitive sheet of the retina called the fovea and this needs to stay balanced to ensure objects of interest can be scrutinised in an optimum way," says Khazali.
They have called this new movement blink-associated resetting movement (BARM) and found that it happens even without a rotating object.
These findings go on to show just how important blinking is for our daily lives. Since we spend about one-tenth of our waking hours blinking, we do it without noticing it. It keeps our eyes lubricated and helps to reduce fatigue.
"To discover such a ubiquitous phenomenon in such a well-studied part of the human body was astonishing to us and we're very grateful to the volunteers who took part in the study," says Khazali.
The findings were published in the journal eLife.