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Variability of fixation disparity and accommodation when viewing a CRT visual display unit
W Jaschinski-Kruza1, E Schubert-Alshuth
1Institute für Arbeitsphysiologie, Dortmund, Germany.
Summary
Fixation disparity and accommodation measurements reveal fluctuations in binocular vision status during prolonged screen use. Repeated testing provides a more comprehensive understanding of individual visual performance.
Area of Science:
- Ophthalmology
- Visual Neuroscience
- Human Factors
Background:
- Assessing binocular vision, including fixation disparity and accommodation, is crucial for understanding visual performance, especially with digital displays.
- Traditional methods may not fully capture the dynamic nature of visual function during sustained tasks.
Purpose of the Study:
- To investigate fixation disparity and accommodation in subjects viewing a cathode ray tube (CRT) at a 50 cm distance.
- To evaluate the reliability and variability of these measurements using a psychophysical method.
Main Methods:
- Utilized the psychophysical method of sequential testing to measure fixation disparity.
- Presented brief dichoptic nonius targets and recorded subject's perceived misalignment.
- Employed laser optometry to measure accommodation relative to stimulus distance.
- Compared two display modes: bright characters on dark background and vice versa.
Main Results:
- Fixation disparity showed a fluctuation range of +/- 1.5 min arc over 5 minutes and +/- 2 min arc over 2 weeks.
- Accommodation lagged behind the stimulus distance by 1-2 prism diopters (D).
- Both display modes yielded similar results for fixation disparity and accommodation.
Conclusions:
- Repeated measurements and psychometric function analysis offer a more complete description of individual binocular status than single adjustments.
- The dynamic range of fixation disparity and accommodative lag are important considerations for visual ergonomics with CRT displays.