Computer Vision Syndrome

• Viewing Distance - Inappropriate viewing distance with the VDT either too close or too far away is another cause of Computer Vision Syndrome. Recommendations for optimum viewing distance vary from source to source. They range from 16 inches to 20 inches to 30+ inches. In practice, proper viewing distance depends on the individual and several other factors:
  • User's Visual Abilities - VDT viewing distance typically falls between the point of optimum near vision and far vision. For younger individuals with good vision and visual accommodation, this is not a problem. However, for users who have vision problems such as near-sightedness (myopia), VDT use may require corrective lens specific for the user's viewing distance.
  • VDT Size - Users tend to sit further away from larger screens which is appropriate so the entire screen is within the field of view. This also serves to eliminate neck movements in viewing the full screen.
  • Character Size - Small characters may require the user to move closer to the display. This, in turn, may require the neck movements to view the full width of the screen. Large character sizes may enable the screen to be moved further away from the user, but will also restrict the amount of information that can be displayed.
• Viewing Angle - The preferred viewing angle is for the user to be centered on the screen with line of sight perpendicular to the screen. Sustained horizontal or vertical off-angle viewing can cause neck, shoulder, and back musculoskeletal complaints. If a workstation has multiple VDTs, the most important information should be displayed on the VDT directly in front of the user. Adjacent VDTs should be easily viewable by swiveling the chair. This enables the retention of the perpendicular line of sight relationship with the screen and helps to avoid repeated neck movements for adjacent VDT viewing.