Abstract: A process for rendering contact lenses made of a polymer or mixture of polymers hydrophilic or increasing their hydrophilic nature comprising generating a beam of positive ions which are essentially of equal kinetic energy, bombarding in an essentially uniform manner the surface of each lens by means of this beam and thereafter hydrating each contact lens; the positive ion beam is obtained by subjecting a gas from the group consisting of nitrogen, oxygen or compounds of these to an electric field produced between a cathode and an anode and in causing part of the accelerated positive ions to pass through the cathode.