PURPOSE. To quantify the levels of protein deposited on Etafilcon (Surevue, FDA group IV, Vistakon) contact lenses when cared for by a polyquad-based multipurpose system (OPTI-FREE Express, Alcon) and a polyhexanide-based system (ReNu MultiPlus, B&L). METHOD. A one-month prospective, double-masked, parallel-group design clinical trial was conducted. Two groups of ten participants wore Surevue lenses for one-month whilst randomly being assigned to a care regimen consisting of either OPTI-FREE Express (using a pre- and post-wear rinsing procedure) or ReNu MultiPlus (using a post-wear rubbing and rinsing protocol). During the wear period, clinical visits occurred at lens dispensing and after 28 days. Following their month of wear, the lenses were aseptically collected and immediately placed in 4mL of extraction buffer, comprising 50:50 acetonitrile:0.2% trifluoroacetic acid. Total protein amounts were assayed using a Micro BCA colorimetric assay, lysozyme levels were determined via electrophoresis and Western blotting using a PhastSystem and lysozyme activity was obtained using a modified Micrococcus lysodeikticus assay.
RESULTS. Clinically, the care regimes demonstrated no significant differences between each other, with similar levels of visual acuity, subjective performance and physiological performance being recorded (p=NS). Subjective ratings of lens comfort reduced (p<0.001) and dryness increased (p<0.001) over the day of wear, regardless of the care regimen being used. Mean total protein concentrations were higher for those lenses cared for with ReNu (2005 vs 1413 µg/lens; p<0.001). This trend was also true for mean lysozyme deposition (1551 vs 935 µg/lens; p<0.001). The amount of denatured lysozyme was also higher following disinfection with ReNu (28% vs 21%), although this result was not statistically significant (p=0.053).
CONCLUSIONS. These results demonstrate that lysozyme deposition on ionic lens materials can be influenced by the care regimen prescribed. Whilst the long-term significance of these results remains unknown, further work to investigate the ability of care systems to denature protein is clearly indicated.