An interior rearview mirror assembly for a vehicle comprises a mirror element and a mirror case having a top surface, a bottom surface, a side surface and a back surface enveloping an interior space. A lamp comprising a light source is positioned and fixedly held preferably in a compartment in the interior space, the light source emitting light when electrically operated. At least one opening is provided in a surface of the mirror case in order to dissipate heat generated by the light source when electrically operated. A light opening is provided in the bottom surface of the mirror case for passing light out of the mirror case into a passenger compartment of a vehicle when the mirror assembly is mounted therein. The light opening in the bottom surface of the mirror case includes a lens positioned therein that directs light emitted by the light source into the passenger compartment of the vehicle; the direction of the light out of the mirror case and into the passenger compartment being non-adjustable with respect to the mirror case. The lens is received by and secures to the mirror case at the light opening and preferably is recessed into the bottom surface of the mirror case.