• rigid gas permeable lens;
  • sodium chloride;
  • free volume;
  • positron lifetime;
  • refractive index


The interaction of sodium chloride with Fluoroperm92 contact lens has been investigated using several techniques. Results indicate adhesion of sodium chloride to the methacrylate and fluorine sites of the lens resulting to zones of excess salt concentration. Na+ and Cl ions appear to be pushed toward the polymer by water molecules, which favor the bulk water structures. Further inference is that lens with more free water leads to localized spots of drying resulting to sites for lipid deposition and lens spoilage. The changes in refractive index of the lens due to salt adhesion correlate well with the free volume. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009