Symptoms appear because the eyes and brain react differently to words on a computer screen than they do to printed text. The eyes respond well to most printed material. Most text consists of bold, black letters on a bright, white background. The eyes can easily focus on images with well-defined edges that are strongly contrasted against their backgrounds. However, words and images on a computer screen do not have well-defined edges. Characters displayed on a computer screen are made up of several small dots, or pixels. The eyes cannot easily focus on pixels, so they must work harder to see the computer screen clearly. The constant struggle to focus leads to fatigue and tired, burning eyes. Many people try to compensate for uncomfortable vision symptoms by leaning forward or by tipping their head to look through the bottom portion of their glasses. These actions can result in a sore neck, sore shoulders and a sore back.
