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Melanopsin is expressed in iris and mediates local pupillary light reflex.
(Left) Melanopsin-immunolabeling in iris cross-sections from wild-type and melanopsin-knockout (OPN4-/-) mice.  Green: melanopsin;  red: smooth-muscle alpha-actin; blue: DAPI.  (Right) Light-induced local pupillary light reflex from isolated mouse iris.