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What causes eye strain?
The medical term for eye strain is asthenopia. The symptoms of ocular fatigue, tired eyes, blurring, headaches, and occasionally doubling of the vision are brought on by concentrated use of the eyes for visual tasks. Some people, while concentrating on a visually intense task such as reading fine print, using the computer for hours at a time, or trying to see in the dark, unconsciously clench the muscles of their eyelids, face, temples, and jaws and develop discomfort or pain from use of those muscles. This may lead to a vicious cycle of tensing those muscles further and causing more distress. Other people attempting to do similar visual tasks may have no symptoms at all.
Common precipitating factors for the onset of eye strain include extended use of a computer or video monitor, straining to see in very dim light, and exposure to extreme brightness or glare. Many people will blink less than normal when performing extended visual tasks. This decreased blinking may lead to dryness of the ocular surface and symptoms of dry eyes.
Refractive errors (a need for glasses for distance or near vision, or both)
may produce the symptoms of eye strain.
The inability to make both eyes work together in a binocular fashion may also generate the symptoms of eye strain. However, most individuals who have limited or no binocular vision have no such symptoms.
In people who already have headaches or blurring of vision due to eye strain, symptoms may be worsened by an underlying eye problem such as an eye muscle imbalance or a need for glasses for the correction of myopia, hyperopia, or astigmatism. In those who already have eye strain, not getting enough sleep, certain medications, being under stress, or being fatigued can also make those symptoms worse.