[The computer screen and vision] [Environmental Optometry] Diana Alrabi

Computer & Vision More than 50 percent of computer users experience eyestrain, headaches, blurred vision and other visual symptoms related to sustained use of the computer. This type of stress on the visual system can also cause body fatigue and reduced efficiency at work. In addition, there are now indications that heavy computer users are at risk for glaucoma

Can A Computer Screen Damage the Eye? extensive testing in government and private laboratories has not produced scientific evidence that computer monitors will harm the eyes. Research has established that computer monitors emit little or no hazardous radiation, such as x-ray, or non-ionizing radiation, such as ultraviolet rays. While computers have no known harmful effects on eyesight, computer users do often complain of eye related symptoms such as eyestrain, headaches, fatigue, dry eyes, and difficulty focusing.

These symptoms (Computer Vision Syndrome - CVS) however are caused not by the computer screen itself but rather by the conditions surrounding the computer screen, such as poor lighting or improper placement of computer equipment and computer furniture. In some instances, a pre-existing eye problem may be the cause..

Computer Stress Computer visual stress may underlie many direct and indirect symptoms. Eyestrain is a common direct symptom, while the need for shifts in posture and muscular strain resulting from poorly arranged work stations cause eye problems indirectly and other physical problems directly.

Computer Stress Direct Computer Stress Symptoms headaches while doing or following computer use irritated and/or dry eyes blurred vision slow refocusing when looking from screen to distance objects frequently losing place when moving eyes between copy and the screen difficulty seeing clearly at a distance after prolonged computer use occasional doubling of vision changes in colour perception changes in glasses prescription

Computer Stress Other Computer Stress Symptoms neck or shoulder tension and pain back pain pain in arms, wrists, or shoulders when working on the computer lowered visual efficiency and more frequent errors

What are the symptoms of computer vision syndrome? If a child spend more than two hours per day in front of a computer screen, it's likely he/she will experience some degree of computer vision syndrome. Symptoms of CVS include: Headaches Loss of focus Burning eyes Tired eyes Double vision Eye twitching Blurred vision Neck and shoulder pain

What causes computer vision syndrome? Computer eye strain and computer vision syndrome are caused by the eyes and brain reacting differently to characters on a computer screen than they do to printed characters. the eyes have little problem focusing on printed material that has dense black characters with well-defined edges. But characters on a computer screen don't have the same degree of contrast and definition.

Words and images on a computer screen are created by combinations of tiny points of light (pixels), which are brightest at the centre and diminish in intensity toward their edges. This makes it more difficult for our eyes to maintain focus on them. Instead, our eyes want to drift to a reduced level of focusing called the "resting point of accommodation" or RPA. eyes involuntarily move to the RPA and then strain to regain focus on the screen. This continuous flexing of the eyes' focusing muscles creates the fatigue and eye strain that commonly occur during and after computer use. What causes computer vision syndrome?

What Can We Do About Eyestrain? Eyestrain will not permanently damage the eyes or cause a loss of vision. However, it can be very uncomfortable and lead to a loss of productivity. Anyone who uses a computer can take measures to reduce eye discomfort.

Get An Eye Exam The American Academy of Ophthalmology suggests that starting with a comprehensive eye exam. This is always a good starting point anytime we experience symptoms like headaches, eye strain, blurred vision, eye irritation, double vision, excessive tears, dry eyes, pain in the eyes, excessive blinking or squinting. The exam will help rule out any ocular conditions that may exist that are causing eye symptoms.

Vision Correction Getting an eye exam is especially important if you wear glasses or contact lenses. Let the optometrist know how often you are in front of a computer screen. Since most glasses are made to correct for a reading distance of 16 inches, it is important that they are adjusted for your particular work environment. It is recommended that the computer screen should be 20 to 26 inches (50-60 cm) from your eyes, and your glasses can be made to accommodate this distance. the glasses can also receive special anti-reflective coatings and tints to help reduce eyestrain.

Vision Correction If the patients are over 40, may require one pair of glasses that corrects for the “normal” prescription and another pair that corrects the vision when in front of a computer screen. If patients are over forty and require reading glasses or wear bifocals (with lines or without), the need for two separate pairs of glasses may be even more necessary. If patient do not normally require a vision correction, computer eyeglasses with low power plus lenses and sometimes a light tint is often helpful. The colour of the tint depends upon the screen background colour, ambient room lighting, and your prescription.

Adjust The Equipment Set the monitor, desk, and chair at comfortable distances and heights. Some of these figures may be obtained in the documentation that came with the computer products. Most users prefer a viewing distance of 20 to 26 inches, but this distance should be between 18 and 28 inches; a little farther away than for reading printed text. The computer screen should be placed slightly below eye level. A good rule of thumb is that the centre of the computer screen should be 4 to 9 inches below your eyes, enabling you to look down slightly at your work. Adjust the brightness of the monitor to an intensity that is comfortable to your eyes; not to bright and not to dim. Then adjust the contrast control so the characters on the monitor and the background so the letters are easily read.

Create Good Lighting And Reduce Glare Try to modify the lighting eliminating glare and harsh reflections. If reading, having the light source coming from behind, over your shoulder, helps to prevent glare problems. If using a computer, dark print on a white or light gray background is less fatiguing to the eyes than multi-coloured print. Sometimes a plastic or glass filter over a computer screen with an anti-reflective coating can help with computer glare. These can be purchased from any office supply store.

Rest Your Eyes Periodically Take frequent, short breaks from near work by focusing on a distance object for a few seconds. Every twenty minutes, get up, stretch your back and neck and look around. Move your eyes and move your body, change your position. Change the distance that you work frequently. If the eyes are feeling increasingly fatigued, hold things further away rather than closer to you. Avoid getting very close to what you are reading.

Avoid Dry Eyes Blink! Studies have shown that when you look at the computer monitor, there is a natural tendency toward a reduced blink rate. The less you blink, the more likely you are to experience dry eye symptoms of burning, sand- in-the-eye, heavy lids, etc. The normal blink rate is averages 12 times per minute. Computer users usually blink 5 times per minute. The longer the eye remains open between blinks, the more likely the cornea is to dehydrate, burn or ache. Then, finally, you blink. But the damage, although minor and easily repaired, is already done. Your eyes sting, burn, sting and otherwise feel miserable. You tear, feel better, then start the process all over again. Eventually, the disruption to the corneal tissue causes a blurred image to go along with the other symptoms. You stop work, fall asleep and your body heals itself until the next time.

There are plenty of non-prescription tear replacement or rewetting drops available at your local drug store but being aware of the need to blink is the real fix, especially if you wear contact lenses.

Thank you