Abstract
Purpose: :
Pre-clinical predictors of clinical performance of contact lens multi-purpose solutions (MPS) would be invaluable R&D tools and are of interest to regulatory bodies. The purpose of this study was to determine whether direct cell-contact or agar-overlay in vitro (MPS) cytotoxicity scores (per USP methodologies) correlate to published in vivo staining, a sign of MPS cytotoxicity.
Methods: :
Six-well cell culture plates were seeded with L929 cells and incubated to 80-90% confluency. New ACUVUE 2 (AV2) and PureVision (PV) hydrogel lenses were soaked in 3.5, 10 or 100 mL of MPS care products, in triplicate, in lens cases or containers for up to 140 hours. Lenses were removed with no saline soak or wash and placed by direct contact, along with 0.8 mL 1XMEM with 5% calf serum, on a monolayer of L929 cells without or with agar overlay. After incubation at 37° C for 24-36 hrs, cytotoxicity was scored by zone of cell death under or around the sample, with no cell death having a score of 0, some under the sample a score of 1, cell death limited to under the sample a score of 2 and cell death beyond the sample a score of 3 or 4. Scores were compared to published data for in vivo corneal staining.
Results: :
A 3.5-mL, 96-hr soak of AV2 lenses in OPTI-FREE Express MPS and ReNu with MoistureLoc MPS produced cytotoxicity scores of 3.3 and 2.0 (direct contact), respectively. Corresponding 1-day % staining scores are 2% and 25%, indicating a negative correlation between in vitro and in vivo tests. A 10-mL, 140-hr soak of PV lenses in OPTI-FREE RepleniSH MPS and ReNu MultiPlus MPS produced cytotoxicity scores of 2.0 and 0.0 (with agar overlay), respectively. Corresponding 1-day % staining scores are 7% and 73% and long-term % staining scores are 14.2% and 37%, also indicating a negative correlation between in vitro and in vivo tests. A 100-mL, 96-hr soak of PV lenses in OPTI-FREE RepleniSH MPS and COMPLETE MPS EASY RUB FORMULA produced cytotoxicity scores of 3.0 and 0.0 (direct contact), respectively. Corresponding 1-day % staining scores are 7% and 15%, again indicating a negative correlation. Overall, a lack of correlation was found between the in vitro and in vivo assessments.
Conclusions: :
No relationship was observed between either direct cell-contact or agar-overlay in vitro cytotoxicity scores of MPS and in vivo MPS staining. These in vitro tests are not reliable predictive tools for MPS clinical staining performance.
Keywords: contact lens • cell survival • cornea: epithelium