The invention provides a locking device for locking two matching lens cell halves of a lens cell. In particular, the invention resides in clips which are located at the joint where the two cell halves mate. The clips, which are molded as part of each cell half, are each comprised of a male member which is inserted into a female member. The male member includes a flexible tab which is deflected when inserted into the female member. After insertion, it is maintained in a deformed state, that is the tab is maintained by the female member so that it is bent from its original position. As a result, a bending moment is induced and maintained in the tab and that moment pushes the tab against an outer wall of the female member. Consequently, forces are established which lock the male member in place. Additionally, the wall of the female member exerts a force on the tab and that force, which is inwardly directed, serves to lock together the two halves and ensures retention of the lens units within the lens cell.