The commonest visual disorder of children is amblyopia (lazy eye), which affects 2-4% of the population. This project explores potential avenues for treating amblyopia in adulthood. Amblyopia is defined clinically as a deficit in visual acuity despite optimal refractive correction, due to some disruption of normal visual development during childhood. Amblyopia is usually treated by occlusion therapy (covering the good eye for a period of time to enforce the use of the amblyopic eye). The effectiveness of this procedure decreases with age. To date, it is not possible to restore normal vision in an amblyopic eye after the age of 8 years, the end of sensitive period of cortical plasticity. This project aims at restoring visual cortical plasticity in adulthood. We know that in the adult brain, the ability of neurons to form new connections is limited by a mesh of molecules surrounding them, the extracellular matrix, which becomes more and more rigid during adolescence. We plan to infuse enzymes into the visual cortex that will loosen up that matrix, and additional substances that are known to promote the outgrowth of neuronal processes. We hope that this combination strategy will reverse the loss of functional connections from the deprived eye to the visual cortex. We will employ functional brain imaging to assess whether visual cortex responses to stimulation of the amblyopic eye will have returned. We will test and refine our treatment using animals, and later on hope to develop it further for amblyopic patients who have suffered loss of vision in their good eye through illness or injury and have therefore become blind or severely visually impaired.