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It's a thing of common sense that if you read, drive or look at computer screen for too long your eyes will get tired. They burn, itch and try to close all the time.

But I was wondering which part(s) of them need rest so much... Blinking muscles? Lense muscles? Or the eyeball is drying out?

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These symptoms have a name: Computer vision syndrome. Basically our eyes are made to look at longer distances from 1-6 meters without much accommodation. Typically computer screens are located at a much closer distance (30-50cm), which requires constant accommodation by the eye. This leads to high stress on the muscles in the eye which subsequently get tired. Additionally less blinking leads to drier eyes.

One of the common recommendations against this is to regularly focus further located objects to give the eye the chance to relax. This is sometimes called the "20-20-20" rule, every 20 min focus on a 20 feet (about 6 m) far object for 20 seconds. See the article in the Wikipedia and here for more information (and probably also the linked references in the articles).

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Was there any success using lenses to make screen appear 6 meters away? – Tomáš Zato Jun 20 '14 at 8:57
This would be like you sit 6m away from you screen: It would most like be too tiny to read anything. – Chris Jun 20 '14 at 9:03
You could sure make it look 6meters high using proper optics. I heard screens in fighter aircrafts are on the cockpit and appear to be on the sky, so that the pilot does not need to change focus. – Tomáš Zato Jun 20 '14 at 9:27
Then you need to turn the head quite a lot to read everything. And my guess for the screens in fighter jets is that they are further away than the typical computer screen. – Chris Jun 20 '14 at 10:23
This doesn't answer the question of which muscles are getting tired. – J. Musser Jun 26 '14 at 2:00

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