Abstract: The support comprises dismountable fixing means for mounting the optical unit on an annular member, which are provided as members made of rigid and resilient wire, each one comprising a linear portion forming a rotation axis, engaged within a corresponding bearing provided in the peripheral portion of the annular member, and two extensions extending on either side from the linear portion and bent transversely with respect to the latter one of the extensions called "inner extension" corresponding to the inner edge of the annular member and being provided at its end with a hook which can be resiliently engaged below said edge in view of its locking, while the other extension called "outer extension" carries at its end a bent portion oriented towards the central portion of the annular member when the inner extension is in the locking position, and the outer extension being, in this position, in close-contact with the outer face of the optical unit.