Adaptive Responses of Accommodation and Vergence Following Exposure to Augmented Reality in a Head-Mounted Display.

Purpose: The vergence-accommodation conflict in augmented reality head-mounted displays (AR-HMDs) can alter the oculomotor system, leading to visual discomfort and fatigue. The purpose of this work was to evaluate changes of accommodation and vergence and their interaction after completing a visually and cognitively demanding 3D task using an AR-HMD.

Methods: Oculomotor parameters, including tonic accommodation (TA), CA/C ratio, tonic vergence (TV), and AC/A ratio were assessed with a photorefractor in 16 participants (10 females; mean age, 23.0 ± 2.6 years). Measurements were taken before and after performing physical and AR versions of an executive function 3D task (Tower of London). Participants moved spheres between pegs at 0.4 m to match the configuration presented on a 2D monitor at 4 m, creating vergence and accommodation demands of 2.5 and 0.25 MA/D. Accommodation demand of virtual content in the AR-HMD, however, remained fixed at 0.5 D.

Results: Oculomotor parameters differed across tasks for TA, F(2, 81) = 9.640, P < 0.001, and CA/C ratio, F(2, 84) = 9.720, P < 0.001, but not for TV, F(1, 81) = 0.485, P = 0.488, and AC/A ratio, F(2, 90) = 0.001, P = 0.99. TA and CA/C ratio reduced significantly post-AR task (P < 0.01) but not post-physical task (P > 0.05).

Conclusions: The AR task induced changes in the CA/C ratio and TA, but no such changes were observed after the physical task, suggesting that exposure to visually and cognitively demanding 3D tasks in an AR-HMD can, at least temporarily, alter the oculomotor system.