When first introduced, computers were almost exclusively used by adults. Today, children increasingly use these devices both for education and recreation. Millions of children use computers on a daily basis at school and at home. Visual demands in school stress the fundamentals of binocular vision, especially when there is an emphasis on the VDT viewing environment. The process of coordination between binocular vision and the accommodative, or focusing system is under constant stress. Studies have found that the convergence system, where the eyes turn in toward each other as the object moves closer, plays a significant role in vision stress. Additionally, the eyes should turn down, as well as in when they view a close object. This results in a normal near viewing posture which is duplicated optimally with book reading. The viewing of a near object at a raised, or eye-level as is often seen in VDT environments, is awkward and unnatural. Visual stress can affect all areas of performance.

COMPUTER VISION SYNDROME

Computer use has grown significantly in the last 40 years. The first computer was developed in about 1950 (when it occupied an entire room) and it is now as commonplace as a telephone. There are currently about 80 million Americans using computers regularly at work. That amount is expected to grow to 100 million by the year 2000. And now with the growth on the Internet, this projection may need to be revised upward.

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. The eye care community has also seen a jump 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 (CVS).

According to the AOA definition, 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 are a combination of improper classroom conditions, poor work habits and existing refractive errors. Lighting, vision and posture are all inter-related concepts. We are visually-directed creatures and will alter our posture to alleviate stress on the eyes. Therefore, paying attention to body posture may be a 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 smoothly and easily focus 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. A child who is 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 strain, even when clear vision can be maintained.

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. Since 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.

CLASSROOM LIGHTING

Lighting is one of the most overlooked and under-emphasized 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 the student 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. Lighting and vision are interdependent factors and must both be considered when designing a classroom environment for maximum efficiency. It is imperative that we increase the awareness and knowledge of how lighting can and will affect school work.

Visual headaches most often occur toward the front of the head (there are a few exceptions to this), occur most often toward the middle or end of the day, do not appear upon awakening, often occur in a different pattern on weekends than during the week, can occur on one side of the head more than the other, and other more general symptoms.

An important factor that affects our ability to see well in the classroom is the quality of light. Good quality light creates good visibility and visual comfort. This can be accomplished with attention to brightness, contrast, quantity of light and color of light. Contrast between a task object and its immediate background must be sufficient to enable the student to clearly view the task. Discussion of 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 effectively see the task. Comfortable light levels will vary with the individual. Comfortable light levels will also vary with 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 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 adjustments of the eye 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. The many factors involved with deciding which lamps and/or lighting products and how to choose them should be discussed in detail when designing classrooms.

Lighting for the classroom of today is distinctively different from what has been acceptable in the past. 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, as compared to 100 foot-candles or more in previous non-computerized offices. Many classrooms have no task lighting, yet task lighting systems are advanced, versatile and available to illuminate work surfaces and tasks without creating veiling reflections or glare on VDT screens or work surfaces.

Many people inquire about the "best" colors for working on a VDT. The actual color of the letters and screen are a secondary consideration in this respect. More important is the contrast between the letters and the background. The combination which offers the maximum contrast is black letters on white background (like paper). This is very disappointing for many people, especially considering that they often have 16 million colors from which to choose! Be cautious of working on pale letters or very dark backgrounds in too bright of an environment.

Lighting a classroom for maximum efficiency is a nice concept. However, in the real world of budgets and bottom-lines, 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 which must be balanced to achieve the most for the money spent. Approximately 86 percent of the cost of lighting is energy consumption, while only 3 percent of the cost is the price of the lamp. Therefore, purchasing cheaper lamps does not necessarily indicate a cost savings. A more prudent method is to purchase lamps which consume power more efficiently.

Recommendations regarding good classroom lighting are threefold: 1) Learning to observe the types of lighting available to the student and to develop ongoing awareness of how this may or may not be working; 2) Identifying risk factors, such as glare and reflections, and the many options for correction of 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-lamping- the cost effectiveness of replacing all lamps when they reach 2/3 of their life expectancy; new classroom design- the cost savings and benefits of doing it right the first time; retrofitting- replacing parts and pieces of existing fixtures as opposed to replacing the entire system; ballast functions- the importance of maintaining the control center of the fixture; lamp options- the many varieties of colors and energy-efficient types of lamps that are available; beam control- using lenses that direct the light to the desire patterns, should all be discussed in detail.

GENERAL EYE CARE TIPS

Here are some things to consider for students using a computer:

	Have the child's vision checked. This will make sure that the child can see clearly and comfortably and can 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 ten-minute break every hour will minimize the development of eye focusing problems and eye irritation caused by improper blinking. Also consider shorter, more frequent breaks.
	Carefully check the height and arrangement of the computer. 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 foot stool 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 may be turned to prevent glare on the screen. Draw curtains or blinds to reduce window lighting. Sometimes glare is less obvious. In this case, 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 computer 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 is very simple 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 onto 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.

Eye health hazards have been touted for many years as a potential concern. As of today, there has been no proof that VDT use causes any type of eye health hazard. The electromagnetic radiation that comes from the VDT monitor is well below all international standards and recommendations. There is more of a concern for this radiation which is emanated from the sides and rear of the monitor. Some eye care professionals feel that a UV protection is necessary for safety while working at a VDT. However, the research has failed to confirm that UV radiation has any effect on the VDT user. Most UV radiation drops off at about four inches from the front of the screen.

Contact lenses are also considered a concern for VDT users, however with very little attention those concerns can be easily addressed. Blinking is a problem for general VDT users and even more so if contact lenses are to be worn. Studies have shown that people blink less often while performing visually intensive tasks, and even less yet while viewing a VDT task. These results are probably a combination of concentration on the task and the position of the monitor. Most often monitors are higher in the visual field of view, therefore allowing the eyes to be open wider. This position is not our natural reading posture and will allow the eyes to dry out faster- with less blinking. This is even more critical for contact lens wearers. The use of lens re-wetting drops is recommended periodically during the day while using a VDT. If the doctor feels that wearing contact lenses is right for the student, then it should be fine for VDT use.

The information presented here is very difficult to obtain for most student populations. Eye doctors generally don't have the time, knowledge or inclination to discuss these issues while examining a patient in an office setting. Additionally, performing eye examinations in an office setting bear very little relationship to the school environment of today's students. A unique and popular software program which actually performs a vision screening on the student's own computer screen is available to perform more accurate testing procedures.

The effectiveness of the student is dependent on adequate visual function and visual function is dependent on appropriate lighting. The two areas are essentially inseparable in their interaction and critical in their effect on classroom performance. Knowledge in these fields is still growing and many professionals are uninformed about this information which is essential for classroom effectiveness and productivity. Today's human factors professional must address this critical area of human performance as it relates to educational technology.