Adhesion of tear proteins to contact lenses and vials

Tear-protein adhesion to contact lenses contributes to lens contamination and deterioration, and depends primarily on the type of contact-lens material used. Adhesion of tear proteins to contact lenses and glass vials was examined using spectrophotometry, hydrophobic-interaction HPLC and bicinchoninic acid (BCA) protein assay. Using spectrophotometry at 280 nm, vials containing two proteins (lysozyme and milk lipocalin) at three different concentrations were examined for changes in their protein concentrations over a 3-week period. Vials containing 5.0 mg/ml lysozyme lost about one-third of their protein (P<0.005), while vials containing 5.0 mg/ml milk lipocalin lost two-thirds of their protein (P<0.01). Conversely, vials containing 1.0 mg/ml lysozyme lost two-thirds of their protein (P<0.005), while vials containing 1.0 mg/ml milk lipocalin lost one-third of their protein (P>0.05). Subsequently, lysozyme deposition on both glass vials and contact lenses was monitored for 5 days using spectrophotometry, to determine lysozyme content in the vials, and HPLC, to determine lysozyme deposition on contact lenses stored in the same vials. This experiment indicated considerable variation in lysozyme deposition on vials and contact lenses, with vial deposition remaining relatively constant (P>0.05) while lens deposition decreased and then increased (P<0.05). Finally, the same experiment was repeated, monitoring lysozyme deposition using the BCA assay. This experiment yielded the most consistent results, with lysozyme deposition on vials continuing throughout the 5 day experiment (P<0.05), while deposition on lenses again decreased and then increased, although to a much lesser extent than in the previous experiment (P>0.05).