Simulated disparity and peripheral blur interact during binocular fusion

Abstract

We have developed a low-cost, practical gaze-contingent display in which natural images are presented to the observer with dioptric blur and stereoscopic disparity that are dependent on the three-dimensional structure of natural scenes. Our system simulates a distribution of retinal blur and depth similar to that experienced in real-world viewing conditions by emmetropic observers. We implemented the system using light-field photographs taken with a plenoptic camera which supports digital refocusing anywhere in the images. We coupled this capability with an eye-tracking system and stereoscopic rendering. With this display, we examine how the time course of binocular fusion depends on depth cues from blur and stereoscopic disparity in naturalistic images. Our results show that disparity and peripheral blur interact to modify eye-movement behavior and facilitate binocular fusion, and the greatest benefit was gained by observers who struggled most to achieve fusion. Even though plenoptic images do not replicate an individual’s aberrations, the results demonstrate that a naturalistic distribution of depth-dependent blur may improve 3-D virtual reality, and that interruptions of this pattern (e.g., with intraocular lenses) which flatten the distribution of retinal blur may adversely affect binocular fusion.

On the number of perceivable blur levels in naturalistic images

“…Held et al (2012b) responded by noting that in 3D scenes a 2D strategy is generally available. Although adding gaze-contingent dioptric blur to stereoscopic natural images reduces the time to fusion and vergence instability including blur in these images decreases stereoscopic acuity because it removes high spatial frequencies that are necessary for fine depth discrimination (Maiello et al, 2014). However, because blur increases with distance from the plane of accommodation (i.e., objects closer to the observer’s plane of fixation or further from it) the sign of blur must be available to be useful.…”

“…Recently, (Maiello et al, 2014) examined fusion and vergence in stereoscopic images of natural scenes captured with a plenoptic camera. The addition of gaze-contingent dioptric blur, proportional to the real depths of objects in scenes, reduced the time to fusion and vergence instability.…”

Three-Dimensional Binocular Eye-Hand Coordination in Normal Vision and with Simulated Visual Impairment

“…Both binocularly symmetric and asymmetric blur impair vergence tracking in depth. In vergence eye movements, the images projected onto the foveae of the two eyes need to be aligned and thus high spatial frequency content in the two eyes is required to be matched [78,50,40,54]. The vergence system is also tightly linked to the accommodation system, which attempts to minimize visual blur at the fovea of both eyes [22,40].…”

“…This could have impacted eye tracking data quality, since the eye-tracker viewed the observer's eyes through the shutter-glasses. However, this method has been successfully used in our published gaze-contingent display [54] and saccadic adaptation [56] studies, both of which required highly accurate binocular eye movement recordings. In addition, simulating depth through shutter-glasses can potentially decouple vergence and accommodation [75,37,99], which might induce additional noise in the vergence-accommodation system.…”

“…Spering et al [85] have found that reduced contrast impairs pursuit eye movements by affecting the correct estimation of target speed while reducing spatial frequency has no systematic effect on pursuit eye movements. Conversely, the precision of binocular alignment is known to depend on spatial frequency [78,40,54]. Thus, both smooth pursuit and vergence eye movements are likely to be impaired by symmetric blur in each eye.…”