INFLUENCE OF CONTACT-LENS MATERIAL SURFACE CHARACTERISTICS AND REPLACEMENT FREQUENCY ON PROTEIN AND LIPID DEPOSITION

The aim of the study was to quantify the influence of both contact len s material and replacement frequency on protein and lipid deposition. The following hypotheses were tested: (1) both protein and lipid inter action with contact lenses are material-dependent, and (2) the key fac tors are the material ionicity for the protein deposition and the mate rial chemical composition for the lipid deposition. Three high water c ontent contact lens materials were tested: netrafilcon A (FDA group II , Gentle Touch), etafilcon A (FDA group IV, Acuvue), and vifilcon A (F DA group IV, Focus), Contact lens spoilation was analyzed using ultrav iolet spectroscopy and fluorescence spectrophotometry, The results sho wed that (1) significantly more proteins were deposited on the ionic m aterials than on the nonionic materials, and that among the ionic mate rials, the higher the ionicity, the higher the level of protein deposi tion; (2) there were significantly more surface proteins on the ionic materials after 3 months than after 1 month of wear, but no difference over time was demonstrated for the nonionic materials; and (3) signif icantly more lipids were deposited onto the surface of vifilcon A than etafilcon A or netrafilcon A, and the presence of vinylpyrrolidone in the vifilcon A formulation was thought to be the cause of increased d eposition. The protein and lipid interactions with contact lenses were found to be material- and time-dependent. Protein attraction was foun d to be related to the material ionicity, The presence of vinylpyrroli done was a key factor in the attraction of lipids.