Asthenopia (aesthenopia) or eye strain is an ophthalmological condition that manifests itself through nonspecific symptoms such as fatigue, pain in or around the eyes, blurred vision, headache and occasional double vision. Symptoms often occur after reading, computer work, or other close activities that involve tedious visual tasks.
When concentrating on a visually intense task, such as continuously focusing on a book or computer monitor, the ciliary muscle tightens. This can cause the eyes to get irritated and uncomfortable. Giving the eyes a chance to focus on a distant object at least once an hour usually alleviates the problem.
On a computer, a CRT with a low refresh rate (less than 70 Hz) can cause similar problems because of the flickering image. Aging CRTs also often go slightly out of focus, and this can also cause eye strain. LCDs do not go out of focus and are less susceptible to visible flicker.
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Sometimes, asthenopia (aesthenopia) can be due to specific visual problems, such as uncorrected refraction errors or binocular vision problems like accommodative insufficiency or heterophoria.
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