Beginning with Johannes Gutenberg in the 15th century, mankind has grown to increasingly depend on the printed word for education, entertainment and much of the world’s work. Five centuries later, we face a change of equal magnitude as the written word has moved into electronic media. Like early printing, our new electronic media suffers from several problems. These include poor resolution, decreased contrast and poor readability. Here are several tips to reduce eyestrain and fatigue when using computers.
Contrast refers to the difference in the amount of light reflected to your eye between the darkest part of the page (the print) and the lightest part (the paper). Early printed works on relatively primitive paper had contrast ratios that were probably on the order of 70% to 80% while modern print has contrast in the 90% range. The best computer monitors do not achieve contrast that is equal to common print output on bright white paper. Optimize contrast by using black fonts on white backgrounds. Adjust brightness and contrast controls to maximize sharpness.
Screen reflections have an extremely negative effect on contrast. You can test your monitor by wrapping a piece of cardboard around the monitor so that the screen forms the bottom of a box. This should keep light from hitting the screen and increase contrast. If this test noticeably improves the clarity of the text on your monitor, you should work to reduce reflections by turning screens away from windows and other light sources. Reducing the amount of overhead lighting and providing a desk light to help when reading from paper will often improve the situation. Even wearing a dark colored shirt or blouse can help reduce the brightest reflections. If you have ever watched a space shuttle launch you may remember the subdued room illumination in the control room. This lighting helps the equipment operators who are all using various computer displays.
The ornate style of Gutenberg’s fonts actually made the text more difficult to read. Descended from his type styles, the simpler serif font is usually best. Serifs are the thickened ends of letters seen on many fonts such as the ubiquitous Times Roman. When reading, our brain has learned to pick up the patterns of darker areas formed by the serifs to improve the speed and ease with which we can decode whole words. Use font sizes that are easily readable. Most people can achieve this by doubling the vertical height of letters they can just barely read. On my monitor, I can just barely read 6 point type so I double the size to 12 point, a common default size.
When viewing high contrast highly readable fonts on bright white paper, we can actually be quite lazy about maintaining our focus on the print. Even when the text is slightly out of focus it is still quite readable. As the reading environment gets more challenging due to decreased contrast, poor font design, or screen reflections, we are forced to maintain a more accurate focus on the work. This additional work translates into more effort on the part of the visual system resulting in eyestrain and headaches at the end of a long workday. For patients who suffer eye fatigue and headaches at the end of the day, a specialized prescription for computer glasses can reduce symptoms by reducing the focusing effort required.
While bifocals do provide power for focusing near objects like computer monitors they have some significant drawbacks for computer use. In order to see through the bifocal, users often find themselves tipping their head back to see through the near portion of the lens leading to neck and shoulder pain. For patients who must wear a bifocal at the computer, it is important to lower the monitor as much as possible. Remember that raising your chair also has this effect. I recommend that the top of the monitor be below the users nose. Take care however that this new position does not compromise other aspects of your ergonomic situation such as hand and wrist position. In my office, we have had great success prescribing a new style of workstation lens that provides broad straight ahead intermediate powers for the monitor and increased near power for reading.
