Reduced visual acuity and stereopsis are common symptoms of amblyopia. Previous studies have demonstrated that motor function is also impaired in patients with amblyopia. Binocular training methods may improve not just visual acuity of the amblyopic eye, but stereopsis and motor function. This pilot study investigated how a binocular contrast discrimination training method may improve these functions in patients with amblyopia, and compared their thresholds to a control group. Furthermore, the differences between amblyopic patients with alternate fixation and those without it were investigated. Patients with amblyopia underwent five sessions of training, each lasting around 90 min. Participants viewed a dichoptic stimulus through a stereoscope, forcing them to fuse the images and use both eyes co-operatively. Participants saw Gabor patches in two successive trials, with a target Gabor shown in only one interval for the non-dominant eye. The dominant eye saw a mask Gabor patch for both intervals. Participants continually were tasked with determining which had the higher contrast until a threshold was reached. Results varied depending on the type of amblyopia, as two of the four patients had alternating fixation. Some patients showed improvements in visual acuity and/or stereopsis, but there were no overall improvements in motor function. This training may be beneficial, even for patients with strabismus who have difficulties with consistent fusion.

We investigated whether visual processing in two-dimensional (2D) space also works in three-dimensional (3D) space using virtual reality (VR) on head-mounted displays, to examine the feature integration theory. In Experiment 1, participants performed a visual search task using 3D items in VR. The search gradients were flat for color-feature search and steep for shape-feature and conjunctive searches. In Experiment 2, two objects with the same visual angle were presented at different distances in VR, and participants from Experiment 1 performed a distance discrimination task using binocular depth cues. Results showed that the shorter the observing distance and the larger the distance difference between the two objects, the more accurately participants discriminated, suggesting 3D perception in VR. In Experiment 3, to investigate whether the inefficiency in shape-feature search in VR was due to retinal heterogeneity among the distractors, other participants performed a visual search task using 3D items on a 2D monitor and showed more efficient shape-feature search. We discussed this result within the framework of the guided search model and concluded that visual processing revealed in 2D also works in 3D.