Visual acuity was evaluated in rd10-nontreated, rd10+MMF mice, and rd10+PTZ mice ages P21, P28 and P41; a cohort of wild-type (WT) C57Bl/6J mice (Jackson Laboratories) were also included in the assessment for comparison. Acuity was measured as described previously30 (link) following the method of Prusky et al.31 (link) Spatial thresholds for optokinetic tracking of sine-wave gratings were measured using the OptoMotry system (CerebralMechanics, Medicine Hat, Alberta, Canada). Mice were placed unrestrained on a pedestal and were presented vertical sine-wave gratings moving at 12°/s or gray of the same mean luminance within the OptoMotry device, which functions as a virtual cylinder. The cylinder hub was continually centered between the mouse's eyes to establish the spatial frequency of the grating at the mouse's viewing position as it shifted its position. Gray color was projected while the mouse was moving; when movement ceased, the gray was replaced with the grating. Grating rotation under these circumstances elicited reflexive tracking, which was scored via live video using a method of limits procedure with a yes/no criterion as recommended by the manufacturer. A measure of spatial resolution was taken as the asymptote of a staircase procedure. The two eyes were tested in an interleaved fashion.