Abstract
When viewing the world, we perceive a stable upright image. This upright perception is maintained despite our eyes, head, neck, and body continuously moving. When the head tilts, the eyes roll in the opposite direction of the head tilt and this reflex is called ocular counter-roll (OCR) or torsion. Tilting the head typically increases errors in upright perception which can be measured using the subjective visual vertical (SVV) task. It has been shown that convergence suppresses OCR when looking at near objects. Here we wanted to take advantage of new virtual reality technology to study the interaction between head tilt and convergence on perception of upright and ocular counter-roll. Three subjects were tested using the FOVE VR headset. We used a subjective visual vertical (SVV) task to measure their upright perception while simultaneously recording torsional eye position at three head positions: upright, head roll 30 degrees left, and head roll 30 degrees right. At each of the head positions we also tested SVV at two vergence distances: near (25 cm) and far (1.5 m). We scaled to maintain constant size in degrees of visual angle at different distances. In the current configuration we did not observe a difference in the amount of ocular counter-roll observed with head tilt during near and far viewing. Perception of upright also did not appear to differ between viewing conditions and head tilts. Our results may suggest that the mechanisms by which near viewing suppresses OCR may not apply under the current VR configuration.