Affiliations: Unit of Optometry, Department of Clinical
Neuroscience, Karolinska Institutet, Stockholm, Sweden | Division of Ophthalmology and Vision, Department of
Clinical Neuroscience, Karolinska Institutet, St. Erik Eye Hospital, Stockholm,
Sweden | School of Technology and Health, Royal Institute of
Technology, Huddinge, Sweden
Note: [] Corresponding author: Susanne Glimne, Unit of Optometry,
Department of Clinical Neuroscience, Karolinska Institutet, Box 8056, 104 20
Stockholm, Sweden. Tel.: +46 8 123 238 19; Fax: +46 8 672 3846; E-mail:
susanne.glimne@ki.se
Abstract: OBJECTIVE: To introduce fixation disparity variance as an objective
measure of visual discomfort. A higher variance in fixation disparity is
indicative of more visual fatigue. This observation is based on the results
from a study where we investigated how fixation disparity was affected by glare
on a VDU. Participants. In total 16 subjects with normal vision participated in
this study. METHOD: In a balanced repeated-measurement experiment, all
subjects performed equal near-vision tasks. In addition to the condition of no
glare three controlled conditions of glare were used: direct light, indirect
light, and desk luminary. After each condition, the fixation disparity was
measured 15 times using a computerized fixation disparity test. RESULTS: The results showed that the average (mean) disparity was found to increase
towards esophoric (crossed) with the adversity of the lighting conditions, but
the differences were not significant. However, when analyzing the variation
(standard deviation) within the 15 measurements and comparing these between
conditions, we found that the direct light condition resulted in significantly
higher variation compared to lighting condition of no glare and desk luminary
lighting. CONCLUSION: Based on these findings, we argue that fixation
disparity variance may be a useful objective measure of visual fatigue.
