The conjunctival and contact lens bacterial flora during lens wear

The conjunctival bacterial flora in wearers of hydrophilic, hard and silicone lenses and in a non-lens control group has been studied. Cultures were also taken from the posterior surface of the various contact lenses. Coagulase negative staphylococci were the most commonly occurring microorganisms both on the conjunctiva and on the lenses. Further identification of these bacteria showed Staph. epidermidis to be the predominant species. Compared with control group a significantly increased frequency of negative conjunctival cultures was found among the lens wearers (P = 0.020). The occurrence of coagulase negative staphylococci was reduced, but the difference was not statistically significant (P = 0.08). Gram-negative bacilli were more frequently found during lens wear (P = 0.012), but were mainly species which are traditionally regarded as apathogenic. The possible influence of lens disinfection, duration of lens wear and eye/lid hygiene on the conjunctival bacterial flora is discussed.