GIVING GROUNDS FOR PHYSIOLOGICAL-ERGONOMIC ACTIVITIES AIMED AT REDUCING EYE FATIGUE CAUSED BY WORK WITH VISUAL DISPLAY TERMINALS
The research was performed on occupational groups which combined visual display terminals (VDT) users. Basic occupational activity of such workers was information input and information read-out from a screen. Constant visual work with a display is a risk factor which can cause health disorders. It makes for visual analyzer strain which becomes apparent through decrease in accommodation as a result of changes in the closest and the farthest point of clear vision. As period of work with a screen becomes longer, fatigue grows, and visual analyzer performance decreases. There are other signs proving eye fatigue; they are changes in temporary characteristics of clear vision stability which are determined by a period of successive contrast perception, and critical fusion frequency which reflects the central nervous system instability. Long-term visually stressful work with VDT causes strain in the body systems which provide visual process. Non-mobile forced "sitting" position can also cause decrease in physical efficiency. Research which was conducted on workers who had to spend more than 4 hours a shift at VDT in their working environment helped to reveal a dependence between their overall physical efficiency and changes in visual analyzer during a shift. The lower workers' physical efficiency was (both male and female), the greater accommodation decrease was detected in them. It is shown that visually stressful work performed by people with low physical efficiency can make for transfer of strain evolving during a shift into overstrain. To prevent eye fatigue as well as overall one in VDT users, it is necessary to work out complex preventive activities which include work and rest regimes; preventive measures aimed at vision strain relieving; correction techniques which help to improve physical efficiency; rational workplace organization.