Loss of antibacterial preservatives from contact lens solutions during storage.

The preservative content of 34 commercially available contact lens solutions has been determined. Over half of the solutions contained less than 90% of the stated preservative content. Storage tests conducted at 40 degrees, using both simulated and commercially available contact lens solutions in plastics containers of the type used to present these products showed that thiomersal and chlorbutol appeared to be sorbed by these containers in contrast to benzalkonium chloride and chlorhexidine gluconate which interacted mainly by a surface adsorption process. The extent of any interactions was dependent upon the type of plastics material used to fabricate the container.