Human-technology interface: Computers & vision health.
Nearly 20 years ago, the American Optometric Association termed computer vision syndrome (CVS) as the complex of eye and vision problems related to near work experienced while using a computer. CVS symptoms reflect the current broad diagnosis of asthenopia (ICD-9, 368.13) also referred to as eyestrain. Symptoms include: fatigue, blurred distal or proximal vision, headache, dry or irritated eyes, neck and/or backaches, blurred near vision and diplopia (double vision). There are two types of eyestrain grouped into internal or external symptoms.
Internal symptoms of CVS are the result of inappropriate ocular motor responses caused by either under or over accommodation relative to an object. Adaptation of the eye for near vision work is accomplished by accommodation; the increase curvature of the lens through movement of the ciliary muscles. An accommodative lag occurs when it takes longer for the eye to change fixation from one point to another. Hence, the accommodative system has to work harder with an increased lag, resulting in visual discomfort and eye fatigue. 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. Furthermore, myopia or astigmatism needs correction to reduce ocular accommodation and minimize the blur to have clear vision of small targets.
External symptoms occur from environmental factors that produce corneal drying, such as low ambient humidity, high forced-air heating, or air conditioning. There is an association between dry eyes and decreased blink rate when performing computer work, reading low-contrast text or small-sized font, and the presence of glare. A reduced blink rate can lead to an increased evaporation of tears, which then exaggerates dry eye symptoms. Dry eye disease (DED) is a multi-factorial disorder of the tear film and ocular surface resulting in discomfort, visual disturbance and ocular surface damage. Any dysfunction of the lacrimal functional unit (LFU) can lead to DED, which causes alterations in volume, composition, distribution, and/or clearance of the tear film. Low aqueous flow or excessive tear film evaporation can be a result of a dysfunction in any of the LFU components, environmental factors, decreased blink rate, and non-modifiable risk factors such as female gender and older age.
It is important to reduce or eliminate risks for developing CVS, thereby maximizing comfort while using visual digital devices. Asthenopia is seldom serious and usually improves with rest, limiting prolonged reading and near work on computers or digital devices, as well as using computer-specific glasses.
The American Optometric Association
* The effects of computer use on eye health and vision. http://www.aoa.org/documents/ EffectsComputerUse.pdf
* Computer vision syndrome symptoms: http:// www.aoa.org/x5375.xml
* Healthy vision at the computer: http://www. aoa.org/documents/Vision-Lifestyle-Fact-Sheet. pdf
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Prevention of Computer Vision Syndrome Routine eye care & exams Corrects vision defects, refractive errors even small astigmatic errors Specific computer glasses may be required to maximize comfort and provide clearer image of the target over time Dry eye therapy Encourage over-the-counter artificial tear solutions, lubricating drops or ointments Consciously blink Forcefully blink, now and then to replenish and lubricate the front of the eyes Rest eyes: the Every 20 minutes look away from the 20-20-20 Rule computer at a distance of 20 feet for at least 20 seconds Properly Arrange Your Computer Work Station Set the location of your * Adjust computer so it is slightly computer below horizontal eye level * Tilt the top of the monitor away from you at a 10[degrees] to 20[degrees] angle, with the center of the monitor below your eyes creating a downward gaze. * It is important that the image on the screen is clear and your head is comfortable Set lighting to avoid glare * Overhead lighting or windows; when sitting in front of a computer light sources are not to be directly visible. * Turn desk or monitor perpendicularly to minimize glare Use correct seating position * Feet flat on the floor with knees bent > 90[degrees] * Chairs that support the legs without excessive pressure on the back of the thighs * Back is snug against the seat, with a thigh-to-trunk angle of > 90[degrees] * Wrists and hands are extended nearly straight from the elbow to the home row of the computer * Keyboard and monitor are straight ahead and the monitor is placed 20 to 26 inches from your eyes Individualize the viewing size * Adjust the Zoom; from 75% to 100%, on the computer or vice versa. Individualize for comfortable reading Change the Font * Veranda is recommended Increase screen resolution & * The better the resolution the clearer the image * The larger the font size the easier to see Adjust contrast and * Not too bright and not too dim brightness Clean your screen * Keep free of fingerprints and dust Place document holders * Place at eye level Eyestrain Internal Symptoms (accommodative External Symptoms (dry eye, stress, convergence stress, or glare, up gaze, small font, uncorrected refractive error) flicker, or environmental factors) * Aches or pain felt inside the eye * Burning * Headache * Ocular dryness * Diplopia (double vision) * Irritation or tearing * Blurring * Strain
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|Title Annotation:||environmental health|
|Author:||Longo, Bernadette; Reese, Christine|
|Date:||Feb 1, 2014|
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