Surprise discovery in the blink of an eye

From eLife:

We probably do it every day, but scientists have only just discovered a distinct new way in which we move our eyes.

The team from the University of Tübingen in Germany assessed the eye movements of 11 subjects using tiny wires attached to the cornea and with infrared video tracking. In results published in eLife, they discovered a new type of eye movement that is synchronised with blinking.

The movement they discovered helps to reset the eye after it twists when viewing a rotating object. It is like avoiding tiny rotations of a camera to stabilise the image we perceive. We don’t notice the eye resetting in this way because it happens automatically when we blink.

“We were really surprised to discover this new type of eye movement and it was not what we had anticipated from the experiment,” says lead author Mohammad Khazali.

“We had expected to find that another, already well-known type of eye movement is synchronized to blinking.”

Although it is brief, blinking creates an interruption in our visual perception. We spend up to a tenth of our waking hours blinking but hardly notice it. It serves an essential role in lubricating the eye and may even provide the brain with small, frequent mental breaks.

The scientists sought to investigate whether a reflexive, involuntary eye movement called torsional optokinetic nystagmus (tOKN) occurs at the same time as blinking. The theory was that this reflex also creates a break in the visual system so synchronising them minimises downtime.

The subjects’ eye movements were tracked as they viewed a rotating pattern of dots. As their eyes twisted to follow the dots, they frequently reset, via tOKN, to avoid moving beyond the mechanical limits of the eye muscles. However, this resetting was imperfect and the eyes gradually twisted until the muscles couldn’t …

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