Relationship between phoria and visual fatigue in autostereoscopic 3D displays

Many people complain about visual fatigue arising from viewing three-dimensional (3D) displays. This paper investigates relationship between visual fatigue and viewers' phoria for viewing autostereoscopic 3D displays. Visual fatigue is evaluated through subjective symptoms with a questionnaire and optometric indicators comprising fusion range as well as accommodation convergence/accommodation (AC/A) ratio to measure the variation in visual functions. A screening test is adopted to divide the subjects into two groups based on whether they suffer from phoria. Then a 2 × 2 × 2 mixed design experiment is conducted with display type, viewing stage, and visual state as factors to examine visual fatigue during viewing session. The results show that phoria subjects obtain more severe visual fatigue than normal on subjective evaluation. The normal subjects reveal a more marked difference with phoria in fusion range and AC/A ratio after viewing 3D video clip. Fusion range can significantly distinguish between the two-dimensional (2D) and 3D condition as well as between the pre- and post-viewing stages. The sensitivity and specificity of fusion range is higher than AC/A ratio with respect to viewing of 3D contents, so it is more appropriate as an optometric indicator of visual fatigue for autostereoscopic 3D displays. This paper investigates the relationship between visual fatigue and viewers' phoria for viewing autostereoscopic 3D displays. Visual fatigue is evaluated through subjective symptoms with a questionnaire and optometric indicators comprising fusion range as well as AC/A ratio. A 2 × 2 × 2 mixed-design experiment is conducted with display type, viewing stage, and visual state as factors to examine visual fatigue during viewing session. The results show that phoria subjects obtain more severe visual fatigue than normal on subjective evaluation. The normal subjects reveal a more marked difference with phoria in fusion range and AC/A ratio after viewing a 3D video clip. Fusion range is more appropriate as an optometric indicator of visual fatigue for autostereoscopic 3D displays.