Medical lens assemblies and sterile drapes with a lens assembly are presented herein. In one embodiment, a lens assembly includes an annular lens housing that is attachable to a medical drape. The lens housing is configured to releasably attach to a medical device, such as a surgical microscope. An annular lens cover holder is removably attachable to the lens housing. A lens cover for shielding the objective lens is pivotably hinged to the lens cover holder. In another embodiment, a drape assembly includes a flexible body sized to cover an optical device. A lens housing attached to the drape body is engageable with the optical device to attach proximate an objective lens thereof. A lens cover holder is removably attached to the lens housing to rotate about a first axis. A lens cover is mounted to the lens cover holder to pivot about a second, different axis.