Fast Recovery of the Amblyopic Eye Acuity of Kittens following Brief Exposure to Total Darkness Depends on the Fellow Eye

Recent studies conducted on kittens have revealed that the reduced visual acuity of the deprived eye following a short period of monocular deprivation imposed in early life is reversed quickly following a 10-day period spent in total darkness. This study explored the contribution of the fellow eye to the darkness-induced recovery of the acuity of the deprived eye. Upon emergence of kittens from darkness, the fellow eye was occluded for different lengths of time in order to investigate its effects on either the speed or the extent of the recovery of acuity of the deprived eye. Occlusion of the fellow eye for even a day immediately following the period spent in darkness blocked any recovery of the acuity of the deprived eye. Moreover, occlusion of the fellow eye two days after the period of darkness blocked any further visual recovery beyond that achieved in the short period when both eyes were open. The results imply that the darkness-induced recovery of the acuity of the deprived eye depends upon, and is guided by, neural activity in the mature neural connections previously established by the fellow eye.