Asthenopia

Asthenopia is the medical term used to refer to the condition more commonly known as eyestrain.

Eyestrain is a term used to refer to the sense of fatigue that can result from prolonged "close work" (intense visual focus on text or objects within 1 foot or 30cm of the eyes, or slightly further away in the cases of certain larger objects).

This is generally worse in cases of:

• insufficient illumination,
• the person already being tired (such as if working late at night), and/or
• the person has an uncorrected error of refraction or an imbalance of the muscles that move and control movement of the eyes.

Eyestrain generally occurs when the muscles that support and operate the eye have been over-used (at that particular point in time, e.g. work session) and are therefore extremely tired. This condition concerns the eyes but, in general, when any muscle is held in one position for too long, the muscle will start to strain. In the case of the eye muscles, over-tired muscles may tighten - resulting in the eyes beginning to hurt and to feel irritated, dry and uncomfortable. Further symptoms of eyestrain can include the sensation of "buring eyes", blurring vision, and headaches.

Many online articles about eyestrain focus on this condition occuring as a result of long work at computer screens. This is, of course, a common modern scenario. However, the same effects can result from excessive viewing of (especially a close) television, or even from more traditional forms of close-work such as needlework (e.g. tapestry), drawing, writing, examination of specimens (e.g. using microscopes) and so on.