The adsorption of major tear film lipids in vitro to various silicone hydrogels over time

PURPOSE. An in vitro study was conducted to measure the adsorption of major tear film lipids to soft contact lenses over time. METHODS. Commercial balafilcon A (PureVision; Bausch & Lomb, Rochester, NY), galyfilcon A (Acuvue Advance; Johnson & Johnson Vision Care), lotrafilcon A and B (Night & Day And O-2 Optix; CIBA Vision, Duluth, GA), senofilcon A (Acuvue Oasys; Johnson & Johnson Vision Care, Jacksonville, FL) and etafilcon A (Acuvue 2; Johnson & Johnson Vision Care) lenses were all soaked for 14 hours in the dark at 34.5 C in either cholesterol (CH; nonpolar lipid) or phosphatidylethanolamine (PE; polar lipid), tagged with 7-nitrobenz-2-oxa-1, 3-diazol-4-yl (NBD) and N-fluorescein-5-thiocarbamoyl (FITC) labels, respectively. After rinsing, the lenses were measured for fluorescence and the corresponding lipid concentration was calculated from an appropriate standard curve. The lenses were then placed into a fresh 1-mL aliquot of the lipid being tested, and the procedure was repeated for 20 days. RESULTS. In vitro adsorption of CH was greater that that of PE for all lens types (P < 0.0001 at days 14 and 20). After 20 days of soaking in PE, the lotrafilcon polymers showed the lowest adsorption of all the silicone hydrogel lenses tested at 0.4 and 1.5 mu g/lens, for lotrafilcon A (P <= 0.0001) and lotrafilcon B, respectively (P <= 0.0001). Galyfilcon A and senofilcon A showed significantly higher PE adsorption at 5.1 and 4.9 mu g/lens, respectively, compared with all other silicone hydrogel lenses investigated (P < 0.03). Senofilcon A (P <= 0.0001) and balafilcon A (P < 0.02) had the highest affinity for CH of all the lens types after 20 days, with adsorptions of 23.2 and 24.1 mu g/lens, respectively. Lotrafilcon B (P < 0.0001) showed the lowest in vitro adsorption of CH of all the lens types, at 3 mu g/lens. CONCLUSIONS. In vitro lipid adsorption varied greatly depending on the lens material for both polar and nonpolar lipids. Overall, there was less in vitro adsorption of lipid to the lotrafilcon A and B polymers than for any of the other silicone hydrogel polymers tested. The quantity of lipid adsorption by lotrafilcon polymers was similar to "conventional" hydrogel lenses.