Studies of intraocular lens sterilization: the effect of NaOH on b. subtilis spores

The Ridley method for intraocular lens sterilization employs 10% NaOH for one hour followed by long-term storage in 0.1% NaOH. Ten percent NaOH for one hour was found to be ineffective when 106 B. subtilis spores were used for study in the presence of a looped lens system. A three-hour period was found to be effective. Similar concentrations of organisms were not killed by 0.1% NaOH even after 30 days. Consequently, the standard Ridley method would be inadequate for looped lens systems and would not fulfill the requirements for terminal sterilization. Teh percent NaOH for three hours would appear to be an acceptable terminal sterilization method.