PURPOSE: To determine the activity of hen egg lysozyme (HEL) deposited on conventional and silicone hydrogel (SH) contact lens materials using an in vitro model.
METHODS: Acuvue 2 (etafilcon; AV2), PureVision (balafilcon; PV), Acuvue Advance (galyfilcon; AA), Focus Night & Day (lotrafilcon A; FND), O2Optix (lotrafilcon B; O2), Proclear (omafilcon A; PC), and Acuvue OASYS (senofilcon A; AO) contact lenses were deposited in vitro in a phosphate-buffered solution (PBS) containing 2mg/ml HEL. Lenses were briefly rinsed in PBS to remove unbound material and extracted in a mixture of acetonitrile and trifluoroacetic acid. Following lyophilization, extracts were examined for lysozyme activity by micrococcal assay and total protein by Western blot.
RESULTS: In terms of total protein accumulation, AV2 showed the most, with 1800µg/lens, PC the next with 68µg/lens and FND the least, with 2µg/lens. AA, AO, and O2 accumulated similar amounts of lysozyme, at approximately 6µg/lens. Lysozyme deposited on AV2 exhibited the greatest activity (91±5%) and this was statistically different from all other lens types (p<0.001). Lysozyme deposited on FND (24±5%) and O2 (23±11%) exhibited the lowest activity. Lysozyme deposits on other lens materials exhibited intermediate activity (AA, 60±15; AO, 51±9; PV, 58±8; and PC, 38±3%).
CONCLUSIONS: Silicone hydrogels deposit lower amounts of lysozyme than either conventional FDA group II (PC) or group IV (AV2) lenses and the levels of activity of the lysozyme are highly variable between materials.
ADDITIONAL COMMENTS: Support: NSERC Canada