UC Berkeley

Advances in technology allow us to track gaze across multiple environments, from the laboratory to the natural world as well as in virtual reality. This has far reaching basic and clinical implications. This dissertation explores both. Our eyes are constantly in motion, helping us piece together a coherent visual perception of the natural world around us. Even during fixation, when the eyes are focused on an object of interest, tiny fixational eye movements shift the position of the image landing on the retina. Our oculomotor system is adapted to the regularities in our natural world, and as a result our visual system functions quickly, comfortably, and accurately in the natural environment. Previous work has shown oculomotor behavior is abnormal in visual disorders such as amblyopia. Chapter 2 of this dissertation describes a study to measure fixational stability in children with amblyopia currently undergoing treatment. This work demonstrates that fixational eye movements can be used as a nonverbal metric for the recovery of visual function in amblyopia. Chapter 3 measures the statistics of fixation and binocular disparity in the natural environment as well as virtual reality (VR) headsets. This work suggests that there are key differences in the statistics of fixation and disparity between the natural and VR environments. The vertical horopter and natural disparity statistics show a top back pitch in the natural environment. This top-back pattern is lacking in the disparity statistics of the virtual environment, and the differences are quite dramatic (in the lower visual field the natural environment has disparities that are much nearer than in VR, an effect of around 900 arcsec!). We additionally found that gaze is biased towards straight ahead viewing and farther fixation distances in VR, as compared to the natural environment. Chapter 4 follows up on the findings from the third chapter, and tests whether observers prefer content that is congruous with the statistics of the natural world in virtual reality. This work found that scene content that violates the top-back pitch pattern of the natural world leads to more discomfort. This suggests that the mismatch between the statistics of the natural and VR-environment documented in chapter 3, is leading to conflict and discomfort in VR headsets.