A half-century of research on the consequences of monocular deprivation (MD) in animals has revealed a great deal about the pathophysiology of amblyopia. MD initiates synaptic changes in the visual cortex that reduce acuity and binocular vision by causing neurons to lose responsiveness to the deprived eye. However, much less is known about how deprivation-induced synaptic modifications can be reversed to restore normal visual function. One theoretically motivated hypothesis is that a period of inactivity can reduce the threshold for synaptic potentiation such that subsequent visual experience promotes synaptic strengthening and increased responsiveness in the visual cortex. Here we have reduced this idea to practice in two species. In young mice, we show that the otherwise stable loss of cortical responsiveness caused by MD is reversed when binocular visual experience follows temporary anesthetic inactivation of the retinas. In 3-mo-old kittens, we show that a severe impairment of visual acuity is also fully reversed by binocular experience following treatment and, further, that prolonged retinal inactivation alone can erase anatomical consequences of MD. We conclude that temporary retinal inactivation represents a highly efficacious means to promote recovery of function. A mblyopia is a widespread form of human visual disability that arises from imbalanced visual experience in the two eyes during infancy or early childhood. The core pathophysiological process underlying amblyopia is ocular dominance plasticity in the primary visual cortex (V1). Ocular dominance plasticity, evolutionarily conserved in mammals with binocular vision, has become a classic paradigm for studying how brain development is influenced by experience and deprivation. A brief period of monocular deprivation (MD) during early postnatal life causes functional depression of synapses in V1 that serve the deprived eye (1-7). Consequently, early-life MD severely and persistently degrades visual acuity through the deprived eye, which typically fails to recover spontaneously when binocular vision is restored (8-10). A critical step in developing targeted interventions for treating amblyopia is to identify strategies for reversing deprivation-driven synaptic modifications in V1.The traditional approach to promote recovery following MD has been to occlude the strong eye to force vision through the weak amblyopic eye. This "reverse occlusion" approach has been validated in animals (11, 12) and represents the cornerstone of current treatment (patching therapy) of human amblyopia (13-16). However, this treatment has well-known limitations that include poor compliance, potential loss of vision through the newly patched eye, failure to recover binocular vision, and a declining treatment efficacy with age (15, 17-21). Nevertheless, the success of reverse occlusion strategies demonstrates that severely weakened synaptic inputs in the brain can be rejuvenated under appropriate circumstances.An insight into how reverse occlusion might promote recovery came fr...