A selenating reagent obtained by reacting lithium aluminum hydride with selenium powder in an organic solvent. Accordingly, in the VCM, power is not additionally consumed in order to maintain a specific position of the lens in a state that a focus of the lens is adjusted. The invention also relates to pharmaceutical compositions including said compounds as well as their use as medicaments. The stylet includes: a central core carrying at its distal extremity the aforementioned coupling mechanism, and at its proximal extremity a handling body for handling by the physician and a hollow tube axially placed around the core.