Adult Opn4Cre/+;Rosa26CAG-tdTomato-eGFP/+ mice (8–10 weeks) were anesthetized with isoflurane. The virus (Addgene plasmid pAAV-hSyn-Flpo, # 60663, (Xue et al., 2014 (link)), packaged into AAV2 at the NINDS Viral Production Core Facility) was placed on a piece of Parafilm and loaded into a glass microcapillary (Fisher Scientific, Cat. No. 11714) pulled needle (Sutter Instruments, Model P-2000). The glass needle was used to puncture the sclera of the right eye and 1.5μL of virus was injected into the vitreous chamber (Drummond Science Nanoinject II, Cat. No. 3–000-204). After 410 the injection, mice were recovered from anesthesia and placed back into their home cages.