The Computer Terminal and Your Eyes - Computer Vision Syndrome (CVS)(Monitor Fatigue)

Are you one of the millions of computer-users for communication, entertainment, business or to access information from around the world? As statistics would have it, 60-90% of software professionals suffer from visual fatigue at some time or the other.

It is certainly hard to deny their convenience at home and in the work place, however, are all of those hours in front of the computer taking a toll on your health and vision? While working with a computer will not ruin your eyes, it may well be putting stress on your visual system. Perhaps you have experienced some of the symptoms of eye stress, strain, or fatigue. If so, read on to discover what may be causing that fatigue and how to alleviate some of the symptoms without compromising your computer use.

Eye Strain?

You're not alone. Over 75% of all computer users report some form of visual discomfort while using their computers specifically their visual display terminal (VDT). The symptoms are unpleasant, but the causes, like improper lighting, glare, and screen brightness, can be easily reduced or eliminated.

Here are some of the common symptoms;

1. Headaches.

2. Blurry or double vision.

3. Itchy burning eyes/irritation/grittiness.

4. Eye fatigue.

5. Excessive tearing or dry sensation in the eyes.

6. Frequent blinking and/or squinting.

So, what causes these symptoms?

A. In the VDT;

1. Improper lighting, glare, reflections on the VDT.

2. A flickering screen.

3. The size of the displayed characters.

4. Colour, contrast and brightness of the screen.

5. Improper design of the workstation.

B. In the eye;

1. Reduced blink rate.

2. Refractive errors/Presbyopia.

3. Prolonged time spent at the computer terminal.

What is really happening

Six groups of external muscles control the movement of the eye. These extra-ocular muscles, as they are known, help to move the eye sideways and up and down, to converge or diverge on an object of focus. An internal muscle, the ciliary muscle, helps focus the lens of the eye. The external and internal muscles work in unison with each other.

So what has age got to do with it?

However between the ages of 35 and 45, the lens becomes less flexible and the ciliary muscles can't adjust the lens focus as they previously could do for objects at a distance of 12 to 20 inches. This condition is called Presbyopia and individuals with Presbyopia usually need reading glasses or bifocals. Even the pupil has a group of muscles which controls its dilation and constriction. A change in light levels from a white, brightly-lit page to a dark computer screen can tire these muscles. Over time and with this stress, the brain can grow fairly tired of trying to interpret what it is seeing via the optic nerve. All of these factors contribute to a physical fatigue of the visual system.

If you are over 40, and in some cases under 40 as well, you may be wearing a bifocal, trifocal or progressive add-on prescription. However, wearers may have to adjust their heads or bodies to a position where they can see clearly through the bifocal or trifocal. This may not be comfortable and can add stress or contribute to fatigue. Also, the portion of the lens that provides the focus that one needs for a certain distance may not provide a wide enough viewing area and, therefore, can be unconformable.

To avoid this eye stress, a stiff neck, or back pain, the patient or computer-user may consider getting a pair of single vision lenses where the entire lens prescription provides clear vision at the distance of the computer. Another option is a bifocal in which the top of the lens is focussed for the computer and the bottom for close reading. You can discuss the specific demands of your job with your optometrist/eye specialist and determine the type of glasses or contacts that are right for you.

If your occupation demands long hours at a computer station, you might ask your employer if your benefits package includes occupational glasses. Your increased efficiency and satisfaction as an employee will quickly compensate your employer for his or her investment in your eye comfort.

Look around you. How is your workstation arranged? The number of factors contributing to the environment of the computer-user is significant, and all of them could contribute to stress, strain and fatigue.

Is there a remedy for this?

Of course there are several;

1. Eliminate glare by moving lights reflecting in the VDT. (Access the source of the glare while the screen is turned off).

2. Get an anti-glare screen if you do not already have one. Anti-glare screens can easily be attached to the front of your VDT much like clip-on sunglasses can be put over a pair of prescription glasses.

3. Draw shades (curtains) and use lower wattage bulbs, and less fluorescent lighting near the computer. In a small room, for example, the lighting should be equivalent to about 60 Watts and the VDT should be perpendicular to bright light sources.

4. Adjust the contrast control on your monitor so that the intensity of the characters is comfortable, generally about 5-10 times brighter than the background. Pay attention also to the size of the fonts in your programs, increase the size to a comfortable view, or magnify the size of the text - using zoom if permitted by the program. Black characters against a white background, as in some of the popular word processors can cause a lot of eyestrain over a period of time due to the excessive contrast. Use a more soothing combination, like a dark background color, and light gray fonts.

5. Adjust the brightness so that the flicker on the VDT is less noticeable. The brightness of the screen itself should be overall 3-4 times the room illumination. It may be worth noting that the flicker is more noticeable with a white background. Move hardware with magnetic fields away from the monitor (transformers, speakers, etc).

6. The position of the monitor is important as well. If the VDT is placed at a level so that you do not have to move your head sideways, or far too high or low, you can work comfortably for a long time.

7. Do get your eyes tested for any refractive errors. Some diseases of the eye may cause repeated changes in near vision requirements, especially glaucoma. So if your working conditions are ideal, it is very important that you get a complete eye check-up done to rule out other eye-related causes of ocular discomfort.

8. Rest - encourage short breaks, which could be used to either close or rest the eyes. An effective exercise is to look away from the screen periodically for a few seconds/minutes.

9. Use of supplementary eye lubricants may be advised by the ophthalmologist in special cases.

These few changes could make a considerable difference when combined with other important elements of the workstation, such as location and general environment and the refractive status of your eyes.

Happy Computing!

Compiled from various sources, by Dr. Ravin Das, M.S., Ophthalmology.
Date: December 16, 1998. Last modified April 7, 2001.

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The term squint to the ophthalmologist means strabismus, or mal-alignment of the visual axis of the eyes. In general terms the word is used here not in the medical context, but to describe a state of screwing of the lids, so as to make the aperture of the lids narrow, while attempting to see something attentively.

Reduced blink rate is because of a very simple natural phenomenon. Whenever we observe anything with much curiosity, or are engrossed with something, the rate at which the eyelids should blink reduces (the normal blink rate is 14-20 times per minute). This in turn causes the normal secretions to dry up, which is accentuated by dry air-conditioning, and also in the dry summer air. This causes the sensation of dry eye, which may present as a pricking in the eyes, or even a red eye. On the other hand the eyes may get watery, due to a reflex excess production of tears.

Refractive errors of the minor types are easily overlooked, since they do not cause much blurring of vision as far as near objects are concerned. However there are minor refractive errors of the type known as astigmatic errors, which cause a lot of strain with both distance vision and near vision, to the extent of headaches. Myopia in the young does not cause as much eyestrain as do Hypermetropia and Astigmatism.

The age at which a person may need Presbyopic correction varies with the refractive power requirements for distance vision. A person with normal distance vision (6/6), will require reading glasses for a comfortable near vision by the age of 40. Whereas, a person who is previously hypermetropic, may require the near correction at an earlier age. And someone who is Myopic may not need any correction provided the myopic correction is in the range of -1 to -2. It is of interest to note here that the usual correction given for presbyopia is measured at a distance of 33 CMS, which is the usual distance at which the keyboard is placed. The monitor may be at a distance greater than 33 CMS, so a special "intermediate" correction may have to be given. The later is the origin of "intermediate-near" distance bifocals for computer users.

Incorrect positioning of the monitor inadvertently worsens CVS. Keeping the monitor at a level higher than neck aggravates the problem because in "up-gaze", the exposed eye-surface area is much larger (almost 2.5 times more) than when the eye is looking down at the monitor. The more the eyes are covered by the lids, the less the evaporation - hence wetter the eyes and lesser the symptoms of CVS. These complaints are often associated with headaches and neck and arm discomfort.

Other factors, like the resolution of the VDT and the refresh rate are also of importance. But it is a far too complex topic, which will not be in context here. Briefly, go for a reputed monitor, take a trial, sit at the monitor for some time before making a purchase. Black and White or Color? The choice is yours, and depends on your budget. The color monitors are definitely packed with more features for more comfortable computing.