|Reprinted from The
RSI Network - Issue 42 - Jan 2000
Adults used computers almost exclusively when they were first introduced. Today, millions of children are using computers every day, at school and at home, for education and recreation. Visual demands in school require the integration of a number of different vision skills: visual acuity (sharpness of vision); visual fixation (eye aiming); accommodation (focusing); binocular fusion (forming a single image); convergence (turning of the eyes); field of vision (side vision); and form perception (recognizing shapes). These systems can be stressed and overworked if not used efficiently. Computer viewing is complicating how children use their eyes in school because these visual skills are not yet fully developed in childrenmaking any near-point activities that much more difficult.
Children can experience many of the same symptoms related to computer use as adults. Extensive viewing of the computer screen can lead to eye discomfort, fatigue, blurred vision, and headaches. However, some unique aspects of how children use computers may make them more susceptible than adults to the development of these problems. The symptoms of physical problems that computer users are experiencing are increasing. Eye doctors have seen an increased in the number of patients who request eye examinations due to symptoms they experience at the computer. This has led to the American Optometric Association (AOA) designation of Computer Vision Syndrome.
Computer Vision Syndrome
According to the AOA definition, Computer Vision Syndrome (CVS) is "the complex of eye and vision problems related to near work which are experienced during or related to computer use." The symptoms that most often accompany this condition are eyestrain, headaches, blurred distance or near vision, dry or red eyes, neck and/or back ache, double vision, and light sensitivity. The factors that most often contribute to CVS in children are a combination of improper classroom conditions, poor work habits, and existing refractive errors. Lighting, vision, and posture are all interrelated concepts. We are visually directed creatures, and will alter our posture to alleviate stress on the eyes. Therefore, ones body posture may be indicative of a visually stressful situation. Some of the symptoms of CVS actually concern the head, neck, and shoulder areas of the body.
The potential impact of computer use on children's vision involves the following factors: Children often have a limited degree of self-awareness. Many children keep performing an enjoyable task with great concentration until near exhaustion (e.g., playing video games for hours with little, if any, breaks). Prolonged activity without a significant break can cause eye focusing (accommodative) problems and eye irritation.
Accommodative problems may occur as a result of the eyes' focusing system "locking in" to a particular target and viewing distance. In some cases, this may cause the eyes to be unable to focus smoothly and easily on a particular object, even long after the original work is completed.
Eye irritation may occur because of poor tear flow over the eye due to reduced blinking. Blinking is often inhibited by concentration and staring at a computer or video screen. Compounding this, computers usually are located higher in the field of view than traditional paperwork. This results in the upper eyelids being retracted to a greater extent. Therefore, the eye tends to experience more than the normal amount of tear evaporation, resulting in dryness and irritation.
Children are very adaptable. Although there are many positive
aspects to their adaptability, children frequently ignore problems that would be addressed
by adults. Children who are viewing a computer screen with a large amount of glare often
will not think about changing the computer arrangement or the surroundings to achieve more
comfortable viewing. This can result in excessive eye-strain. Also, children often accept
blurred vision caused by nearsightedness (myopia), farsightedness (hyperopia), or
astigmatism because they think everyone sees the way they do. Uncorrected farsightedness
can cause eye
Children are not the same size as adults. Since children are smaller, computers don't fit them well. Most computer workstations are arranged for adult use. Therefore, a child using a computer on a typical office desk often must look up further than an adult. Because the most efficient viewing angle is slightly downward about 15 degrees, problems using the eyes together can occur. In addition, children may have difficulty reaching the keyboard or placing their feet on the floor, causing arm, neck, or back discomfort.
Lighting is one of the most overlooked and underemphasized components of our indoor environment. Whether working at the computer or in a warehouse arena, our field of vision needs to be free of reflections and sources of glare. Our lighting needs to prevent problems, not cause them. Lighting is effective when it allows us to see the details of a given task easily and accurately. Comfort in lighting is a very individual concern, and must be addressed on a one-to-one level; no one lighting pattern will work for every working situation. Those in charge of classroom lighting need to learn what is available to help them make the right choices for the students. As lighting and vision are interdependent factors, both must be considered when designing a classroom environment for maximum efficiency. It is imperative that we increase our awareness and knowledge of how lighting affects schoolwork.
Poor lighting can be a source of visual headaches, which most often occur toward the front of the head (there are a few exceptions to this), or toward the middle or end of the day. They do not appear upon awakening, often occur in a different pattern on weekends than during the week, and can occur on one side of the head more than the other. Other symptomssuch as eyestrain, tired eyes, double vision, and red or dry eyesare more general.
An important factor that affects our ability to see well is the quality of light. Good-quality light creates good visibility and visual comfort, and involves brightness, contrast, as well as the quantity and the color of light. Contrast between a task object and its immediate background must be sufficient to enable the student to clearly view the task. The contrast ratios involved in classroom lighting should be considered so rooms can be set up to maximize productivity without increasing eyestrain.
Too much or too little light can inhibit the student's ability to see the task effectively. Comfortable light levels will vary with the individual as well as the task. The more rapid, repetitive, and lengthy the task, the more important it is to have enough light. With these types of tasks, the eye is more vulnerable to fatigue and the student or worker to declined productivity. Children often use computers in a home or classroom with less than optimum lighting. The lighting level for the proper use of a computer is about half as bright as that normally found in a classroom. Increased light levels can contribute to excessive glare and problems associated with adjusting the eyes to different levels of light.
Different colors of light will create different moods or atmospheres that will affect a student's sense of well-being and level of productivity. Color-corrected lights come closest to nature's light, imitating the color rendition of the noonday sun and adding a whole new sense of well-being to the classroom environment. This can be achieved by altering the lighting sources, or installing a special filter that can be placed between the lens and lamp of a fixture, or fit as a sleeve over each lamp. People designing classrooms, especially for computer use, must understand a number of important factors that should affect the choice of lamps and/or lighting products.
Classroom lighting that was acceptable in the past is no longer acceptable today. The average ambient light levels in most classrooms are too high, too inefficient, and too costly. The trend now calls for reduced ambient lighting, supplemented by adjustable task lighting. Recommended light levels for today's computerized classroom is 40-50 foot-candles for ambient light, compared to 100 foot-candles or more in previous noncomputerized offices. Many classrooms have no task lighting, yet readily available task lighting systems are advanced, versatile, and can illuminate work surfaces and tasks without creating veiling reflections or glare on VDT screens or work surfaces.
Lighting a classroom for maximum efficiency is a nice concept. In the real world of budgets and bottom-lines, however, cost effectiveness is also a major consideration. The cost of energy, of new lighting fixtures, of retrofitting, of remodeling, and more are all significant considerations that must be balanced to achieve the most for the money spent. It might help to know that approximately 86% of the cost of lighting covers energy consumption, while only 3% involves the price of the lamp. Therefore, purchasing cheaper lamps does not necessarily lead to cost savings; these are achieved by purchasing lamps that consume power more efficiently.
The following three recommendations will lead to good classroom lighting decisions: 1) Learning to observe the types of lighting available to a student and to develop ongoing awareness of how they may or may not be working; 2) Identifying risk factors, such as glare and reflections, and the many options for correcting these factors; 3) Developing solutions that involve teacher responsibility, administrative cooperation and caring, and realistic cost-effective improvements.
Issues to be considered are: group re-lampingthe cost-effectiveness of replacing all lamps when they reach two-thirds of their life expectancy; new classroom designthe cost savings and benefits of doing it right the first time; retrofittingreplacing parts and pieces of existing fixtures as opposed to replacing the entire system; ballast functionsthe importance of maintaining the control center of the fixture; lamp optionsthe many varieties of colors and energy-efficient types of lamps that are available; beam controlusing lenses that direct light to the desired patterns.
General Eye-Care Tips for Students Using Computers
Have the child's vision checked to ensure that the child can see clearly and comfortably, and to detect any hidden conditions that may contribute to eye-strain. When necessary, glasses, contact lenses, or vision therapy can provide clear, comfortable vision, not just for using the computer, but for all other aspects of daily activities.
Strictly enforce the amount of time that a child can continuously use the computer. A 10-minute break every hour will minimize the development of focusing problems and eye irritation caused by improper blinking. Also consider shorter, more frequent breaks.
Carefully check the height and arrangement of the monitor. The child's size should determine how the monitor and keyboard are positioned. In many situations, the computer monitor will be too high in the child's field of view, the chair too low, and the desk too high. A good solution to many of these problems is an adjustable chair that can be raised for the child's comfort, since it is usually difficult to lower the computer monitor. A footstool may be necessary to support the child's feet.
Carefully check the lighting for glare on the computer screen. Windows or other light sources should not be directly visible when sitting in front of the monitor. When this occurs, the desk or computer should be turned to prevent glare on the screen. Draw curtains or blinds to reduce window lighting. Sometimes glare is less obvious. Holding a small mirror flat against the screen can be a useful way to look for light sources that are reflecting off of the screen from above or behind. If a light source can be seen in the mirror, the offending light should be moved or blocked from hitting the screen with a cardboard hood (a baffle) attached to the top of the monitor. In addition, the American Optometric Association has evaluated and accepted a number of glare screens that can be added to a monitor to reduce glare. Look for the AOA Seal of Acceptance when purchasing a glare-reduction filter.
Reduce the amount of lighting in the room to match the computer screen. Often this can be simply done in the home. In some cases, a smaller light can be substituted for the bright overhead light, or a dimmer-switch can be installed to give flexible control of room lighting. In other cases, a three-way bulb can be turned to its lowest setting.
Children have different needs to comfortably use a computer. A small amount of effort can help reinforce appropriate viewing habits and assure comfortable and enjoyable computer use.
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Last Updated: 11/03/00