"Studies have shown that despite use of MPS [multipurpose cleaning solutions], contamination of lens storage cases remains common, occurring in 30-80% of cases," according to a new post on ContactLensUpdate. "Lens cases have also been shown to be the most frequently and heavily contaminated of all the lens care accessories, including the bottle of disinfecting solution and the contact lens itself. Bacteria and biofilm: Health hazards hiding in lens cases Bacterial growth in a lens storage case is believed to be mostly biofilm; that is, a static adherent group of micro-organisms encased in polymeric material, composed of polysaccharides, proteins, nucleic acids and lipids produced simultaneously by the microorganisms in the biofilm and host cells or fluid. Biofilms are characterized by their resistance to stressful conditions." Read more.