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 includes trimethoprim , a salt of edta and an adjuvant bactericide that is either sorbic acid or ascorbic acid . 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 from the surfaces of soft contact lenses and aids in preventing deposits from forming and binding to the lenses .