ORIGINAL ARTICLE Ex Vivo Protein Deposition on Bi-Weekly Silicone Hydrogel Contact Lenses Adrienne Boone*, Miriam Heynen † , Elizabeth Joyce ‡ , Jalaiah Varikooty § , and Lyndon Jones ¶ ABSTRACT 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 O 2 OPTIX (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 g/lens), with other lenses depositing 10 g/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 g/lens), with other lenses depositing 2 g/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 g/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. (Optom Vis Sci 2009;86:1241–1249) Key Words: protein deposition, lysozyme, silicone hydrogel, surface treatment, protein activity S ilicone hydrogels transmit significantly greater quantities of oxygen to the cornea than conventional hydrogels 1,2 and represent a class of materials that are increasingly being used for patients on both an overnight and daily wear basis. 3,4 Although oxygen deprivation induces a number of hypoxic complications, discomfort, particularly at the end of the day, re- mains the leading cause for discontinuation of contact lenses. 5–9 Silicone hydrogel (SH) contact lens materials have been primarily developed to alleviate complications induced by both acute and chronic hypoxia. 10 –14 However, SH lenses have a higher modulus of elasticity than polyHEMA-based materials, 1,15 increasing the rigidity of the lens and potentially impacting lens comfort. In addition, they have surfaces that are generally more hydrophobic than that encountered with traditional hydrogels 16 –20 and may show compromises in in-eye wettability. In addition to wettability and material stiffness, another factor that may impact on-eye comfort relates to lens deposition with various components from the tear film. Contact lens deposition is known to affect contact lens comfort, vision, and clinical perfor- mance. 21–24 Lysozyme represents a significant proportion of the total protein that is found in tears and is the major protein depos- ited on Food and Drug Administration (FDA) group IV contact lenses. 25–30 It was first shown by Karageozian that lysozyme may be a significant contributor to the problems encountered by con- *PhD † MSc ‡ BSc § BMed, MSc ¶ PhD, FCOptom, FAAO Centre for Contact Lens Research, School of Optometry, University of Water- loo, Waterloo, Ontario, Canada. 1040-5488/09/8611-1241/0 VOL. 86, NO. 11, PP. 1241–1249 OPTOMETRY AND VISION SCIENCE Copyright © 2009 American Academy of Optometry Optometry and Vision Science, Vol. 86, No. 11, November 2009