Determination of the lysozyme deposit curve in soft contact lenses.

PURPOSE: To determine lysozyme deposition as a function of time in soft, high-water content, ionic (group IV) contact lenses.
METHODS: ACUVUE lenses were worn on an extended-wear basis (15 minutes, 2 hours, 4 hours, 6 hours, 8 hours, 1 day, 2 day, and so forth, up to 11 consecutive days). New lenses were dispensed at the beginning of each lens-wear period. After each wear cycle, lenses were analyzed for lysozyme deposition by high performance liquid chromatography.
RESULTS: Lysozyme rapidly accumulated on lenses (15 minutes approximately 55 microg/lens) and reached a plateau level by day 6 ( approximately 1300 microg/lens). Most patients in the study showed a plateau range between 1200 and 1400 microg/lens. Six-month and 12-month follow-up studies with ACUVUE lenses showed minimal variation at the 5-day wear time point between the initial, sixth, and 12th month results.
CONCLUSIONS: This study measured the rate of lysozyme buildup on lenses over time and demonstrated that lysozyme levels associated with group IV lenses reached a plateau after approximately 1 week of extended wear. Little variability was seen in lens lysozyme deposition up to 1 year later. The information derived from this study concerning the rate and variability of deposition has implications for the design and interpretation of cleaning studies and contact lens performance evaluations.