  Between 1 to 5 out of 100 people worldwide has never experienced normotypic
vision due to a condition called amblyopia, and about 1 out of 4000 suffer from
inherited retinal dystrophies that progressively lead them to blindness. While
a wide range of technologies and therapies are being developed to restore
vision, a fundamental question still remains unanswered: would the adult visual
brain retain a sufficient plastic potential to learn how to see after a
prolonged period of abnormal visual experience? In this review we summarize
studies showing that the visual brain of sighted adults retains a type of
developmental plasticity, called homeostatic plasticity, and this property has
been recently exploited successfully for adult amblyopia recover. Next, we
discuss how the brain circuits reorganizes when visual stimulation is partially
restored by means of a bionic eye in late blinds with Retinitis Pigmentosa. The
primary visual cortex in these patients slowly became activated by the
artificial visual stimulation, indicating that sight restoration therapies can
rely on a considerable degree of spared plasticity in adulthood.
