Ex Vivo Protein Deposition on Bi-Weekly Silicone Hydrogel Contact Lenses

PURPOSE: This study investigated the protein deposition that occurs on daily wear silicone hydrogel (SH) lenses, after 2 weeks of wear. METHODS: A total of 40 subjects were divided into equal groups, based on their habitual SH contact lens [CIBA Vision O2OPTIX (O2); Johnson & Johnson ACUVUE ADVANCE with HYDRACLEAR (ADV); Bausch & Lomb PureVision (PV); CIBA Vision Night & Day (ND)]. A randomized, double-masked, cross-over study was conducted in which subjects wore either their habitual SH material or Johnson & Johnson ACUVUE OASYS with HYDRACLEAR PLUS (OAS) for 2 weeks. At the end of the 2-week period, lenses were collected for analysis of total protein, total lysozyme, and percent denatured lysozyme. RESULTS: Total protein was greatest for PV (33 +/- 6 microg/lens), with other lenses depositing <10 microg/lens. The PV amount was greater than other materials (p < 0.001), with no significant differences between the other three materials (p > 0.05). Total lysozyme was also greatest for the PV lens (11 +/- 3 microg/lens), with other lenses depositing <2 microg/lens. The PV amount was greater than all other materials (p < 0.001). ADV and OAS were greater than O2 (p < 0.01) but were not different from each other (p > 0.05). The percentage of lysozyme that was denatured was greatest for ND (90 +/- 8%) and lowest for PV (23 +/- 10%). The lysozyme extracted from ND and O2 lenses was significantly more denatured than that extracted from the other lens materials (p < 0.001). There were no significant differences for lysozyme activity between ND and O2 (p > 0.05) or between ADV, OAS, and PV (p > 0.05). The amount of denatured lysozyme/lens was <3 microg/lens for all materials. Lysozyme as a percentage of the total protein deposited ranged from 32 (PV) to 6% (O2). CONCLUSIONS: This study confirms that all SH lenses deposit low levels of protein, and that the amount and percentage of denatured lysozyme can vary, depending on the overall surface charge of the material and absence or type of surface treatment.