Effects of polarity and ambient illuminance on the searching performance and visual fatigue for various aged users

The study investigated the effects of screen polarity (black-on-white and white-on-black) and ambient illuminance (200 and 500 lx) on the searching performance and visual fatigue for different aged VDT (Visual Display Terminal) users (20-30, 45-54, and over 54 years old). The result of this study showed that the polarity had a significant effect on subjects´ searching performance. Subjects´ searching performance was significantly better at black-on-white polarity than at white-on-black polarity. In addition, ambient illuminance, age, and the interaction between illuminance and age also had significant effects on subjects´ searching performance. Subjects aged over 54 had the better searching performance in 500 lx than in 200 lx; however, the illuminance had no significant effect on searching performance for subjects younger than 55. Regarding the visual fatigue, the effect of ambient illuminance on the subjective visual fatigue was significant. The subjective visual fatigue was significantly higher at 200 lx than at 500 lx.