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Time factors in VDT-induced myopia and visual fatigue: an experimental study
1Vision Laboratory, University of Oslo, Norway.
Journal of Human Ergology
|June 1, 1992
Summary
Continuous video display terminal (VDT) work impairs visual acuity and muscle function. A 15-minute rest period partially restores these functions, with no significant difference between 2 or 4 hours of VDT use.
Area of Science:
- Ophthalmology
- Optometry
- Ergonomics
Background:
- Prolonged video display terminal (VDT) use is common in modern workplaces.
- Concerns exist regarding the impact of VDT work on visual and oculomotor health.
Purpose of the Study:
- To investigate the effects of continuous VDT work on visual acuity, refraction, and oculomotor functions (zone of clear, single vision - ZCSV).
- To evaluate the impact of a 15-minute restitution period on these visual and oculomotor parameters.
Main Methods:
- Two matched groups (n=13, n=17) performed VDT work for 2 or 4 hours.
- Visual acuity, refraction, ciliar muscle capacity, vergence muscle capacity, and ZCSV were measured before and after VDT work.
- ZCSV was reassessed after a 15-minute restitution period.
Main Results:
- Both VDT work durations led to significant reductions in visual acuity, myopic shifts in refraction, and decreased ciliar and vergence muscle capacity.
- The observed changes in ZCSV were temporary.
- A 15-minute restitution period restored approximately 50% of the ZCSV changes.
- No significant differences were found between the 2-hour and 4-hour VDT work groups for any measured variable.
Conclusions:
- Continuous VDT work negatively affects visual acuity and oculomotor function.
- Short rest periods offer partial recovery but do not fully reverse the effects.
- The duration of VDT work (2 vs. 4 hours) did not significantly alter the observed visual or oculomotor impacts.