RGCs in mixed culture are lost via apoptosis. Dissociated cells from adult C56BL/6 mice were cultured for 24 h with 3.3 nm Otx2, 20 μm ZVAD, or both and NF+ RGCs were counted. Otx2 promoted the survival of RGCs as did ZVAD. There was no additive effect of Otx2 + ZVAD (ANOVA, F = 18.674, p < 0.0001; *p < 0.005, Fisher's PLSD). Six coverslips were analyzed for each condition.