[Comparative study on visual fatigue caused by watching liquid crystal display and projection display]

Area of Science:

• Ophthalmology
• Human Factors Engineering
• Ergonomics

Background:

• Visual display terminals (VDTs) are ubiquitous in modern work environments.
• Assessing the impact of different VDT screen types on visual fatigue is crucial for occupational health.
• Previous research has not conclusively compared the effects of projection screens versus flat panels on visual strain.

Purpose of the Study:

• To investigate and compare the effects of different visual display terminal (VDT) screen types on visual fatigue.
• To determine if projection screens (metal, glass bead) induce more visual fatigue than LED flat panel displays.
• To explore potential physiological mechanisms underlying VDT-induced visual fatigue.

Main Methods:

• Sixty-eight subjects were divided into three groups: flat screen, metal screen, and glass bead screen.
• Participants watched a video for 60 minutes under controlled conditions.
• Visual fatigue was assessed using rating scales, visual function tests (including critical flicker fusion frequency and near point of convergence), and blink rate monitoring.

Main Results:

• All VDT types significantly increased visual fatigue ratings, blink rate, and decreased critical flicker fusion frequency (CFF) and near point of convergence (NPC).
• Projection screens (metal and glass bead) resulted in significantly higher subjective visual fatigue compared to LED flat screens.
• Reduced positive fusional vergence was observed in projection screen groups but not in the flat screen group.

Conclusions:

• Short-term VDT use significantly contributes to visual fatigue, potentially due to diminished positive convergence.
• VDT operation using projection screens may induce greater visual fatigue than LED flat panel displays.
• The specific type of projection screen (metal vs. glass bead) did not significantly influence the level of visual fatigue.