Histologic analysis of the retina of the 6-month old ChmFlox (A), ChmFlox, Tyr-Cre+ (B), ChmFlox, IRBP-Cre+ (C), ChmFlox, IRBP-Cre+, Tyr-Cre+ (D) and 12-month old ChmFlox (E), IRBP-Cre+, Tyr-Cre+ (F). (G) Morphometric analysis of the number of photoreceptor rows in the central retina in the ChmFlox, IRBP-Cre+ (purple bars) and ChmFlox, IRBP-Cre+, Tyr-Cre+ (blue bars). Numbers of animals analyzed were: ChmFlox, IRBP-Cre+: 6 to 8 months (n = 15), 12 to 14 months (n = 19); ChmFlox, IRBP-Cre+, Tyr-Cre+: 6 to 8 months (n = 7), 12 to 14 months (n = 11).