Blink, and you'll miss it: New eye movement discovered

September 21, 2016
Key to rewetting ocular surface, blinking holds other vision benefits.

It seems there is more to blinking than meets the eye, as novel research describes a previously unknown, automatic eye movement serving as a visual reset function.

Published Aug. 23 in the biomedical journal eLife, the University of Tubingen (Germany) paper details a specific eye movement synchronized with blinking that helps the eye reset after twisting to view a rotating object. This function, coined a "blink-associated resetting movement" (BARM), helps reduce eye strain as viewers assess their often dynamic environments.

The study sought to determine whether torsional optokinetic nystagmus (tOKN) were synchronized with blinking to minimize interruption of visual perception. To achieve this, subjects' eyes were tracked when viewing a rotating pattern. While tracking, the eyes frequently reset via tOKN to prevent over-rotating beyond the eyes' mechanical limits. Researchers noted this resetting was imperfect, causing the eyes to gradually twist until the muscles couldn't twist any further. Once maximizing their movement, the eyes naturally reset via this BARM.

"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," said lead author Mohammad Farhan Khazali, in a press release.

Shaping our understanding of blinking

Aside from providing much-needed moisture to the ocular surface, blinking also helps protect the eye from irritants and disengages our attention, ever so briefly, to allow the brain to process. Darrell Schlange, O.D., associate professor at Illinois College of Optometry, says clinical evidence also suggests that blinks appear to provide increased intensity of the stimulus for saccades, pursuits, accommodation, vergence and visual attention. "This research investigates the resetting of the tOKN and motor synergy with blinks, thereby reducing the interference in optic flow, enhancing the continuity of visual input and avoiding a decrease in visual processing," Dr. Schlange notes upon reviewing the paper.

Discovery of a consistent, resetting tOKN during a blink supports a conclusion of motor synergy; however, Dr. Schlange says there are alternative theories of this process, such as merely concurrent actions—not synergistic—presented and countered in the paper's experimental findings.

"A primary human goal of improving visual inspection of our environment, without interruption of visual input during blinks, saccades and tOKN, is better understood by this important research finding," Dr. Schlange says, adding the clinical significance of this study is likely limited. 

Screen time and eyes

Although such research likely won't influence chairside conversations, it does provide a more complete picture of blinking, especially as the relationship between digital device use and eyesight is scrutinized. A 2014 study determined that subjects reading from a computer screen versus hard copy were no more likely to blink fewer times for one or the other; however, computer-reading subjects were more likely to blink incompletely. It's an association that might help explain anecdotal evidence of increased eye strain and fatigue, and dry eye from prolonged digital device use.

Just as blinking provides a mental break, the AOA recommends device users follow the 20-20-20 rule (take a 20-second break every 20 minutes to look at something 20 feet away) to provide a visual break from devices and lessen the effects of digital eyestrain. 

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