preservative systems which may be incorporated into aqueous compositions for the daily cleaning of silicone copolymer and soft contact lenses are provided . the preservative system may comprise solely trimethoprim . adjuvant bactericides may also be present , such as a salt of edta , sorbic acid , ascorbic acid or benzyl alcohol . one suitable cleaning composition which incorporates the preservative system includes three types of detergents . the cleaning composition is effective in removing both proteins and lipids and calcium from the surfaces of soft contact lenses and aids in preventing deposits from forming and binding to the lenses .