Many of us feel that the growing use of computers is harmful to our eyes. However, till date there is no convincing scientific evidence that computer terminals are harmful to eyes. Nevertheless, since complaints of eyestrain are becoming common, it would be prudent to pay more attention to safety aspects of computer terminals. At times you may be suffering from eyestrain but it may not necessarily be due to computer terminals. It could be due to the wrong and improper usage of computer terminals. 

Symptoms of eyestrain: 

• Sore, tired, itchy, dry, or burning eyes
• Headaches 
• Difficulty focusing between the monitor and source documents 
• Blurred or double vision 
• Colour fringes/after images 
• Increased sensitivity to light 

These symptoms may have been caused by:

Improper lighting: If the light in the work area is too bright or too dim, your eyes have to strain extra hard to adjust to these factors. You may not even be aware that your eyes are exerting themselves but over a period of time, you may develop symptoms of eyestrain. Use indirect lighting and an adjustable light source at the desk, where extra illumination is required. 

Glare: Glare is caused by sources of light such as windows, lamps, or overhead lighting. Look at your monitor screen to see if there are any bright patches of light. While you may not be conscious of this, it can cause eyestrain over the course of long hours at terminals. Glare can also be caused by too much contrast between the screen background and the displayed text. Adjust your monitor so that it is not reflecting the light source. Tilt the monitor down so that it doesn't reflect overhead lights, or move it perpendicular to windows. Close shades or blinds if the computer cannot be moved. Move lamps so that they are not reflected directly in the monitor. Use glare screens. 

Eyewear: If you wear glasses of any sort and frequently experience headaches while working at a computer, you should probably check with your ophthalmologist to make sure you are wearing the correct prescription for the work you are doing. 

Viewing angle and distance: If your monitor is too far away, you may have to strain to read the print. Likewise, if it is too close, you may also strain your eyes. If the monitor is too high, you will have to angle your neck to look up at it, which could strain your neck and may contribute to headaches. Also, when you are continually looking up, you may not fully close your eyes when you blink, and this can cause your eyes to dry out. Some literature will suggest keeping the monitor between 18-30 inches from the user, with the first line of text just slightly below eye level. 

However, you should always find out what is most comfortable to you. You may also want the keyboard directly in front of the monitor. If the keyboard/monitor is off to one side, the distance to the monitor may be slightly different for each eye, causing them to focus separately. Take micro-breaks! Frequently look up from your monitor and focus on an object several feet away. Make a conscious effort to blink. Some people concentrate so hard that they blink only once per minute, instead of the normal once every five seconds. Uninterrupted focus on the screen too causes the eyes to dry out and become irritated. 

Monitor and document holder location: Place document holder at the same level, angle, and distance as the screen to avoid having to shift eye focus. Dust off your monitor every day. A build-up of dust on the screen can make it hard to distinguish characters. This may also contribute to glare and reflection problems. Some people temporarily notice black and white objects tinged with colour after viewing VDTs for an hour or more (this is called the McCollough Effect). These colours are usually complimentary (opposite) to the colour of the VDT characters, and are not a sign of an eye disease, damage to the eye or eyestrain. So take care and ensure that you are not straining your eyes while reading this article.