Abstract
Purpose :
In augmented reality (AR) displays, the accommodation (A) demand is fixed at a specific distance, while the vergence (V) demand varies according to the distance to the virtual objects, with potential side-effects on the A-V system remaining after removing the MR device. The aim was to investigate V and A responses before and after performing a virtual executive function task in MR.
Methods :
Refraction and gaze responses were measured with a photorefractor (PoweRef3) before and after performing a virtual Tower of London task in AR (Hololens 2, Microsoft) in twenty young adults (20–24 yrs, 11 males) with habitual correction. The task involved using tracked hands to manipulate virtual objects at a 50 cm distance to match a configuration presented on a physical 2D screen at 4 m. Refraction and gaze were measured over one minute while participants alternated between two targets at 40 cm (near) and 4 m (distance) at 3 intervals (10 cycles in total), with instruction to keep the targets focused and fused. V (in meter angle, MA, computed from gaze) and A (in diopters, D, computed from refraction) were compared using the Wilcoxon rank sum test.
Results :
The differences in V and A responses before and after the MR task were calculated. At near, the median(IQR) V and A responses were 0.11(0.50) MA and -0.05(0.33) D, respectively, while at distance they were 0.12(0.26) MA and -0.06(0.25) D, respectively. These differences were significant both at near (Z=291, p=0.015) and distance (Z=316, p=0.001). However, there were individual differences with V and A being either coupled or uncoupled (vergence and accommodation responding in same or opposite directions, respectively). At near, 7 participants had coupled (range 0.03–0.50 MA) while 13 had uncoupled responses (0.10–1.53 MA). At distance, 6 and 14 had coupled (-0.03–1.94 MA) and uncoupled responses (0.14–1.49 MA).
Conclusions :
There are measurable acute effects of the vergence-accommodation conflict after performing tasks in MR displays with V and A remaining uncoupled: 70% of participants exhibited either more convergence while relaxing their accommodation or more divergence whilst accommodating more after doing the task. That V and A remain uncoupled may affect behavior in the physical world after using MR displays. Further work is needed to understand how protracted the effect is.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.