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12-04-2012 | General practice | Article

Orbicularis oculi muscle involved in eyestrain during computer work


Free abstract

MedWire News: Eyestrain that results from physically demanding computer work appears to be related to the orbicularis oculi muscle, research shows.

After 2 hours of visually demanding work on a laptop, muscle load and blood flow increased significantly above baseline in the orbicularis oculi.

"In the first hour of computer work, subjects who developed pain symptoms had significantly higher muscle blood flow compared with subjects with minimal pain symptoms," report Hanne-Mari Schiøtz Thorud (Buskerud University College, Kongsberg, Norway) and colleagues.

Publishing their findings in Optometry and Vision Science, the researchers point out that computer vision syndrome was first identified 20 years ago and includes ocular symptoms, such as dry and tired eyes, blurred vision, and extraocular symptoms, such as pain around the eyes and in the neck and shoulders.

In the present study, the group hypothesized that eye strain might be the result of increased tension in the orbicularis oculi muscle. This muscle is an elliptical sheet that surrounds the eye and extends from the eyelid to the brow, temple, and cheek.

To investigate the development of discomfort symptoms in relation to muscle activity and blood flow, the group studied 20 healthy male and female participants and recorded their eye-related symptoms during a 2-hour working session on a laptop where they were exposed to high glare and a small font.

During the session, the subjects reported eye-related pain and fatigue, blurred vision, itchiness, gritty eyes, photophobia, dry eyes, and tearing eyes.

Using electromyography, the researchers observed an increase in muscle load in the orbicularis oculi with the maximal voluntary contraction increased 1% to 1.5% above baseline.

"Because of increased squinting to avoid the glare during the 2 hours of computer work, the orbital part of the orbicularis oculi muscle contracted," explain Thorud and colleagues.

In the first 40 minutes of computer work, blood flow, assessed with photoplethysmography, significantly increased 20% above baseline and returned to normal in the last 20 minutes of the first hour.

Overall, there was a significant positive correlation between fatigue and muscle activity in the orbicularis oculi, but no association was observed between tiredness and muscle blood flow. By contrast, there was a positive correlation between pain and blood flow, but no association between pain and muscle activity in the orbicularis oculi.

The researchers conclude by stating that the mechanisms responsible for producing pain might differ from the mechanisms underlying fatigue and that further study will be necessary to assess different muscle activity patterns.

By MedWire Reporters

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