People who sit in front of a computer for long periods of time often encounter a variety of uncomfortable symptoms. Headaches, neck strain, backaches and wrist pain are common, but, sadly, the most prevalent symptoms of prolonged computer use- eye strain, blurred vision and dry eye- are often overlooked. The chief physical complaint of people working with computers is visual strain and fatigue. Studies show that 47% of computer workers have eyestrain within three hours of initiating their work.
These symptoms contribute to Computer Vision Syndrome, which the American Optometric Association defines are "the complex eye and vision problems related to near work that are experienced during or related to computer use." Sitting at a computer generally causes a person to look straight ahead for long stretches, work in a dry office or home environment, and to blink less often. These factors can lead to vision problems. Additionally, computer use requires specific vision skills, which add further demands to the visual system and contribute to eye and vision discomfort.
These skills include
Ocular Motility- the ability of the eyes to move in various positions.
Accommodation- the ability of the eyes to focus clearly at various distances.
Vergence- the ability to move the eyes in (convergence) or out (divergence).
On top of the eye's ability to perform, there are several causes from the computer and work environment itself that can cause eye strain.
The computer display screen acts like a mirror, reflecting light or bright colors. It is wise to have curtains over windows, and dark or flat (matte) painted walls. Also, the operator should refrain from wearing white or light colored clothing. Other means of reducing glare are:
* utilizing an anti-reflective screen on the monitor
* changing the angle of the screen by tilting it horizontally or vertically
* moving your station to a different position.
If your desk is of a shiny laminate material, use a matte-finished desk blotter to degrade the reflective quality. A good test to determine whether glare is a problem is to place a 12" X 12" mirror over the screen, keyboard and desk. Sit in your normal position; if you see any of the light or bright sources in the mirror, you are actually demonstrating glare. Try to eliminate or reduce it. Look for glare reduction filters that have received the American Optometric Association Seal of Acceptance.
Proper lighting in the computer environment is very important. Prior to computers, it was recommended that a general office have about 1,000 lux of light. With the use of computers, however, that figure was reduced to 300-500 lux. The prime reason for this reduction in the amount of light is that a sharp contrast between the monitor and the background is a major source of visual discomfort. You may benefit from task lighting, where copy work is illuminated by auxiliary lighting.
The display unit itself should be considered. Make sure that your computer monitor does not have a "ghost" image on the screen, which indicates a problem with phosphene absorption. Increase the resolution to the highest resolution your monitor will support. If the increased screen resolution makes items too small, try increasing the font size (DPI) to compensate.
Adjust the contrast between characters on the monitor and the background so the letters are easily read. Adjust the brightness of the monitor to an intensity that is comfortable to your eyes- not too bright and not too dim.
There is still controversy concerning whether the radiation emitted from the monitor (front and sides) is harmful, but better safe than sorry. We recommend that you have a UV400 (ultraviolet protection) filter included in your computer glasses. This offers you some protection if 6 hours per day, 5 days per week, 50 weeks per year, and 10 years' worth of exposure does prove to be damaging to your eyes or general health.
Another source of visual distress is the flicker in your peripheral field of vision from other monitors. If this is a factor, try to shield these monitors from your peripheral field of view. There should be as much flexibility as possible in the placing of computer components so that they can be adjusted to each operator's specific needs. If the screen has a swim to it (movement of the display), it is best to change to a better monitor. It is most important that the images on the video screen are clear.
Distance from the computer
The average visual working distance for people using computers is 20 inches. If your material (copy, keyboard, screen) are at the same distance of 20 inches, the fatigue factor will be decreased, because there will be less varying focusing demand on your eyes.
It is also important to take a 5-minute break hourly. This greatly benefits your body and mind, as well as your eyes. Look out a window at a distant object or view, or vary your task to another office duty for a while. Visual comfort and efficiency are interrelated; it is to your (and your employer's) benefit to have you as visually comfortable as possible.
Preventive health care includes visual care
One study revealed that there was temporary reduction of vision after three hours of computer work. The patients in the study went from 20/18 (actually better than 20/20) to about 20/25 after three hours at the computer. After they stopped their work, it took about 16 minutes to recover their original 20/18 level. It is not unusual for computer operators to have difficulty in making a visual shift from near to far and from far to near. This complaint may be a predecessor of nearsightedness, of an increasing amount of nearsightedness, or presbyopia, a condition that is improved by the use of reading glasses.
Studies show that with extensive use of computer monitors, people under the age of forty tended to show an increase in the need for reading glasses.
Specially Designed Lenses
Many times this new environment makes it necessary for operators 35+ to get special glasses for near, usually in progressive lens form. Progressives allow the patient to see clearly in the distance, with a gradual change in the prescription to see at near towards the bottom of the lens. There is an intermediate distance in between that allows computers to be clear. Bifocals are not the best option, because they only allow a patient to see at a far distance and reading distance.
Specially designed single-vision lenses, focused for the computer world of about 20 inches, give another alternative that works well. Some new invisible office lenses are specially designed for computers. Ask your opticians about these! Lastly, an anti-glare treatment is mandatory to add to your lenses. These reduce the unwanted glares off of computers and surfaces that can cause eye strain, headaches, and tired eyes. A special blue-light anti-glare treatment is now available which can help even more with eye strain, preventing medical problems such as cataracts and macular degeneration from occurring.
Get your eyes checked
Your eyes should be checked regularly by our optometrists for near visual needs, as well as for distance vision, for these are two different visual-functioning situations. Some studies show that because of evolution from our being outdoor people to becoming very near-oriented people, nearsightedness has increased dramatically in the past eighty years. The higher the visual demand, the more imperative it is to have more frequent care.
Blinking is the windshield wiper of your eyes, and one of its purposes is to evenly and regularly spread tears over your eyes to keep them wet, clear and healthy. Computer operators have been found to blink only 3 times per minute rather than the normal 15 times per minute. Please be aware of this and enhance your blink pattern and rate. Make sure that you follow the 20/20/20 rule. Every 20 minutes, take a 20 second break and blink 20 times. This will keep your eyes feeling more fresh near the end of day.
Workstation setup for comfortable computer use
Feet should be flat on the floor (or on a slightly angled foot rest) with knees bent close to or greater than 90 degrees.
The chair seat should support the legs without excessive pressure on the back or the thighs.
The back should be snug against the seat to fit your spinal contour. The thigh-to-trunk angle should be 90 degrees or greater.
Wrists and hands should extend nearly straight from the elbow to the home row of the keyboard.
Adjust the keyboard tilt angle so that wrists are straight.
A commonly preferred work surface height for keyboard use is about 26" as opposed to the conventional 29" of most tables or desks.
Place the monitor 20-26" from your eyes, depending on the size of the monitor and individual vision conditions.
The monitor and keyboard should be straight ahead.
The top of the monitor should be slightly below horizontal eye level. Tilt the top of the monitor away from you at a 10-20 degree angle. The center of the monitor should be 10-20 degrees below your eyes. This is 4-9" below your eyes at a distance of 24".
Keep the monitor free from fingerprints and dust. Both can reduce clarity.
Place document holders close to the screen within the same viewing distance. Keep the keyboard and monitor in line.