This value is approximately 2-fold greater than the percentage of S-opsin–positive cells identified in wild-type control retinas, 1.65% (54 S-opsin-positive cells out of 3,271 DAPI-positive cells), and accords well with the previously reported value of 2- to 3-fold more S-opsin–positive cells in rd7 compared to wild type arrived at by antibody staining of tissue sections [17].