Some people report visual discomfort when watching 3D displays. For both the objective measurement of visual fatigue
and the subjective measurement of visual discomfort, we would like to arrive at general indicators that are easy to apply
in perception experiments. Previous research yielded contradictory results concerning such indicators. We hypothesize
two potential causes for this: 1) not all clinical tests are equally appropriate to evaluate the effect of stereoscopic viewing
on visual fatigue, and 2) there is a natural variation in susceptibility to visual fatigue amongst people with normal vision.
To verify these hypotheses, we designed an experiment, consisting of two parts. Firstly, an optometric screening was
used to differentiate participants in susceptibility to visual fatigue. Secondly, in a 2×2 within-subjects design (2D vs 3D
and two-view vs nine-view display), a questionnaire and eight optometric tests (i.e. binocular acuity, fixation disparity
with and without fusion lock, heterophoria, convergent and divergent fusion, vergence facility and accommodation
response) were administered before and immediately after a reading task.
Results revealed that participants found to be more susceptible to visual fatigue during screening showed a clinically
meaningful increase in fusion amplitude after having viewed 3D stimuli. Two questionnaire items (i.e., pain and
irritation) were significantly affected by the participants' susceptibility, while two other items (i.e., double vision and
sharpness) were scored differently between 2D and 3D for all participants. Our results suggest that a combination of
fusion range measurements and self-report is appropriate for evaluating visual fatigue related to 3D displays.