In human vision, one eye is usually stronger than the other. This is called ocular dominance. Extremely imbalanced ocular dominance can be found among certain patient groups, for example, in patients with amblyopia. Here, we introduce a novel method to rebalance ocular dominance. We developed an altered-reality system that subjects used to interact with the natural world, the appearance of which was changed through a real-time image process. Several daily adaptation sessions lasting 3 hr each reduced sensory ocular dominance in adults who were not diagnosed with amblyopia and improved vision in patients with amblyopia. Surprising additional strengthening was found over the subsequent 2 months, when subjects experienced natural vision only. Our method effectively trains subjects to use both eyes in the wide variety of everyday tasks. The transfer of this training to everyday vision likely produced the continuing growth in effects during the months after the training. These findings are promising for the application of this method in future clinical research on amblyopia.