Viewing a computer screen often makes the eyes work harder. As a result, the unique characteristics and high visual demands of computer viewing make many individuals susceptible to the development of vision-related symptoms.
Viewing a computer screen is different than reading a printed page. Often the letters on the computer screen are not as precise or sharply defined, the level of contrast of the letters to the background is reduced, and the presence of glare and reflections on the screen may make viewing difficult.
Viewing distances and angles used for computer work are also often different from those commonly used for other reading or writing tasks. As a result, the eye focusing and eye movement requirements for computer viewing can place additional demands on the visual system.
In addition, the presence of even minor vision problems can often significantly affect comfort and performance at a computer. Uncorrected or under corrected vision problems can be major contributing factors to computer-related eyestrain.
Even people who have an eyeglass or contact lens prescription may find it’s not suitable for the specific viewing distances of their computer screen. Some people tilt their heads at odd angles because their glasses aren’t designed for looking at a computer. Or they bend toward the screen in order to see it clearly. Their postures can result in muscle spasms or pain in the neck, shoulder or back.
In most cases, symptoms of CVS occur because the visual demands of the task exceed the visual abilities of the individual to comfortably perform them. At greatest risk for developing CVS are those persons who spend two or more continuous hours at a computer every day.
Source: Ohio Optometric Association