A mechanism for permitting selective adjustment of the angular position of a head-mounted night vision device is provided. The mechanism comprises a housing positioned adjacent the night vision device. A shaft defining a longitudinal axis is at least partially positioned within or adjacent the housing. The shaft is rotatively coupled to the night vision device, wherein rotation of the shaft induces rotation of the night vision device. A moveable lever is coupled to the shaft for rotating the shaft. Means for selectively limiting rotation of the shaft are provided, wherein the means are moveable between a first position and a second position. In the first position the means permit rotation of the shaft and the optical device, and in the second position the means limit rotation of the shaft and the optical device.