Heterophoria adaptation during the viewing of 3D stereoscopic stimuli

In this experiment two hypotheses were tested. The first hypothesis was that viewing 3D stereoscopic stimuli which are located geometrically beyond the screen on which the images are displayed would induce exophoric heterophoria (phoria) changes (adaptation). The second hypothesis was that participants whose phoria changed as a consequence of adaptation during the viewing of the stereoscopic stimuli would experience less visual discomfort than people whose phoria did not adapt.

Twenty participants aged between 19 and 45 were recruited to play a computer game in 3D and 2D conditions for 20 min each. Heterophoria was measured before and after viewing the stimuli, and visual discomfort was assessed by questionnaire on both occasions.

Statistically significant changes in heterophoria were found in the 3D conditions (p = 0.007), but not in the 2D conditions (p = 0.16). The difference between the two conditions was statistically significant (p = 0.035). On average, there were also significant differences in visual discomfort between pre and post viewing, for both 2D and 3D conditions, however not everyone reported experiencing discomfort. The sample was then divided into groups, those who had reported an increase in discomfort whilst viewing 3D stimuli, and those who had not. No significant differences in heterophoria, or heterophoria change, were found between these two groups.

The present study has shown that heterophoria can change as a result of viewing 3D stereoscopic stimuli, a change which is similar to prism adaptation. There was appreciable variability in the magnitude of this adaptation between individuals, but there was no correlation between the heterophoria change and visual discomfort.