The Influence of the Vertical Location of VDT Screen on the Ocular Dryness

ABSTRACT

The fatigue of eye is much caused by eye dryness during VDT work. We performed this study to find out whether eye dryness is reduced wit the computer screen which is placed lower than primary gaze during VDT work. Forty people without eye disease were selected. One VDT screen was placed 5degreesabove the primary gaze(5degreesup screen) and the other 25degreesbelow the primary gaze(25degreesdown screen). We measured the frequency of blinking and vertical palpebral fissure height, at rest and while they enjoyed an interesting computer game for 20 minutes. Tear film break-up time(BUT) was also measured at rest, during and immediately after computer game. At rest, the average frequency of blinking was 22.35+/-6.28/min and BUT was 10.20+/-2.63 seconds. During VDT work with 5degreesup screen, the measurements were significantly decreased to 7.48+/-3.43/min and 5.38+/-1.43/min, respectively. These, however, were improved with 25degreesdown screen showing 10.05+/-4.59/min and 7.00+/-1.55 second(p>0.01). The average vertical palpebral fissure height was 6.49+/-1.07mm at rest, and 9.49+/-1.26mm with 5degreesup screen. With 25degreesdown screen, this was 7.69+/-1.01mm and narrower than the measurement with 5degreesup screen(p>0.01). This study reveals that the visual fatigue from the ocular dryness will be improved with the computer screen placed 25degreeslower than primary gaze and laid adeqately back like in reading position.