Abstract
Introduction: Binocular alignment and depth perception depend on the computation of interocular differences in retinal information. Studies have indicated that we are able to report which eye has been stimulated when the two images are sufficiently different. Here we tested the roles of vergence stability, ocular sensation, and visual perception in identifying the eye of origin. Methods: Dichoptic images (2x3deg) were presented with or without a fusion lock, using a PROPixx projector. Eye movements were recorded with an Eyelink 1000. Cartoons at zero disparity were presented for 1s to both eyes (control condition), one eye, or with simulated anisometropia (2D), for 10 repetitions. In different sessions, 22 participants were asked i) whether they felt an ocular sensation and in which eye and ii) which eye’s image appeared disrupted (i.e., either missing (monocular) or blurred (anisometropia)). Results: Pilot testing confirmed that the fusion lock alone drove and sustained vergence. The standard deviation of the vergence response during the 1s trials indicated no difference across all conditions except for the monocular condition with no fusion lock (p=0.005). GLMM models indicated that participants were significantly more likely to report both an unusual sensation, and a disrupted perception, in the disrupted eye. In both cases, performance was significantly better in the monocular than the anisometropia condition, and when the fusion lock was absent (all p<0.005). Performance was significantly (p<0.05) above chance in 13 of 22 participants individually. Conclusion: Many participants were able to identify the disrupted image. The increase in proprioceptive and visual percepts, and vergence instability, during monocular presentation in the absence of the fusion lock suggests vergence provides a cue, but above-chance performance with a fusion lock suggests visual cues as well. Individual differences in percepts may predict successful use of AR and monovision technologies and dichoptic treatment of binocular vision disorders.