University of Rochester

Video Display Terminals

Video display terminals (VDT's) are used by almost everyone in the workforce. The increased use has raised a number of health concerns including eye strain, ergonomic factors, radiation effects, and reproductive effects.

Eye strain:

Spending long periods of time in front of a computer monitor can cause headaches, blurred vision, and misperception. It is caused by overexertion of the muscles that focus your eyes. When your focus is kept on a VDT screen for a long time, muscles can't move, expand, or rest. Eye strain can be reduced by minimizing the glare on your screen, taking short breaks from the computer, and by changing your focus to a distant object occasionally.

Ergonomic factors:

Ideally, every work station should be completely adjustable so that any individual can make the proper corrections for personal height and comfort. Combinations of having desk tops too high, chairs which are not adjustable or are incorrectly adjusted, and poor work habits can lead to physical problems such as wrist/arm discomfort or back/neck fatigue. The VDT Workstation Checklist is included so that you can assess your own office and make the proper corrections. Besides the furnishings in your office, there are several other factors which will help prevent repetitive motion disorders of the wrists. Work habits play an important role in preventing injury; wrists should be kept aligned (no flexing sideways or resting them on the desk top) and frequent breaks should be taken to perform alternate tasks such as filing. There are several devices on the market to assist the user in developing the proper wrist positioning, more information can be obtained from Environmental Safety.

Electromagnetic fields/Radiation effects:

Studies have shown that the electromagnetic fields generated by VDT's are no greater than fields generated by ordinary appliances. As studies have shown, properly functioning VDT's do not give off x-rays and even the worst malfunctions have generated only insignificant amounts of radiation.

Reproductive effects:

The literature on the effects of VDT use on pregnancy have shown that there are no significant adverse effects on the fetus. However, due to the nature of the hazard, some people have questioned the conclusions of these studies. There are also other variables, such as stress, which complicate the issue.

VDT Workstation Checklist


  • 2 1/2" from table to top surface of space bar.
  • 11" from top of chair seat to keys.
  • less than 2" (ideally 1 1/8") from base of keyboard to home keys.


  • 24-28" from floor (upper and lower arms should form 90o angle).


  • Top of screen at or below eye level.


  • Tilted back 10-20o.
  • Face at right angle to windows and light sources.


  • Adequate contrast.
  • Not excessive brightness.
  • Absence of glare from other sources.


  • Comfortable working height - no excessive pressure on legs.


  • Small of back supported.

VDT Workstation Adjustments


  • Too high - place pads under wrists.
  • Too low - place pad of paper or flat piece of wood under keyboard.


  • Place small wedge under front of monitor.
  • Adjust contrast and brightness controls (pull blinds if window behind).


  • Seated in chair with feet flat on the floor, measure the distance from the hollow of knees to the floor; subtract 1 to 3 inches for correct height for top of chair seat.
  • Use footrest if feet off floor after adjustment.

QUESTIONS? Contact EH&S at (585) 275-3241 or e-mail EH&S Questions.

This page last updated 11/17/2004. Disclaimer.