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fatigue or irritation of the eyes, resulting from excessive use, as from prolonged reading of small print, or uncorrected defects of vision



or asthenopia, a state characterized by a feeling of heaviness in the eyes, a dull pain in the forehead and temples (sometimes expressed as a headache), difficulty in working, diffuseness and indistinctness of previously distinct contours of objects (for example, letters in a text), and a need to close the eyes and rest them.

There are two types of eyestrain: accommodative and muscular. Accommodative eyestrain (overstrain of the accommodation muscle) develops primarily in young people suffering from hyperopia when there is need to study an object at close range for a long time. To avoid eyestrain the hyperopia must be corrected with eyeglasses, and the person must take periodic breaks from work and look into the distance. Analogous phenomena of eyestrain may be observed with uncorrected astigmatism of the eye.

Muscular eyestrain develops predominantly with uncorrected myopia and is caused by a relative weakness of the interior straight muscles of the eye, which effect convergence of the visual lines of both eyes on an observed object; upon closing one eye, all unpleasant sensations disappear. To pre-vent this form of eyestrain the myopia must be corrected, sometimes with the use of prismatic glasses (spheroprismatic lenses), and the person must take periodic breaks from work.


References in periodicals archive ?
Poor workplace conditions such as ergonomically unsound computer tables and chairs and improper work habits can contribute to digital eyestrain, but the condition is primarily caused by the computer screen's stress on the eyes.
Digital eyestrain is irritating, painful and a productivity killer--no question.
Even the imperceptible flicker of the fluorescents can be a source of stress and eyestrain. Add a dimmer switch to control the luminance and try to match the brightness of the lighting with that of your monitors.
In addition, the Adora20 also supports Less Blue Light technology - with as much as 75% blue light reduction - combined with the MSI exclusively-developed ScenaMax image optimization software to effectively reduce the screen s Blue light emission; significantly reducing harmful eyestrain and protecting users eye sight.
The main cause of eyestrain is thought to be fatigue of ciliary and extraocular muscle due to prolonged accommodation and vergence required by near vision work.
* Lighting: Reduce eyestrain by avoiding sun glare and providing adequate light at the workstation.
Therefore, with near vision demands or computer work, accommodation lags and fails to fully relax, thereby causing blurred vision and/ or eyestrain in the person.
The flicker-free light also helps reduce eyestrain, making it the perfect light for reading, needlework and long periods of studying.
The flicker–free light also helps reduce eyestrain, making it the perfect light for reading, needlework and long periods of studying.
To minimize eyestrain, the unit's micro-array lens evens out light refraction for more natural lighting and even distribution.
Extraneous light, otherwise known as glare, is the greatest source of eyestrain to computer users.
Kondrot practices both traditional and alternative therapies for the prevention and treatment of eye diseases, including macular degeneration, glaucoma, cataracts, eyestrain, and much more.