Previously, we have shown that monocular deprivation (MD) in adult mice does not have long-term consequences for spatial vision (Prusky & Douglas, 2003). The recent development of a virtual optomotor system (Douglas et al, SFN, 2003) has enabled us to test the short-term effects on spatial vision of adult MD. MD for a few hours did not affect visual acuity or contrast sensitivity. MD for five days, however, significantly enhanced the acuity of the non-deprived eye. Acuity was up 20% within one day, and it plateaued at 40% above pre-deprivation acuity (~0.4 c/d) after 3 days. Contrast sensitivity in the non-deprived eye also increased by 150 to 300%, depending on the spatial frequency, during the period of MD. When the deprived eye was opened after 5 days, the enhanced visual thresholds in the non-deprived eye began to decrease within a few hours, and returned to baseline levels over the next 7 to 10 days. The acuity of the deprived eye 1 day after the end of MD and beyond was not different than it was befo...