title: In vitro analysis of the physical properties of contact lens blister pack solutions.
abstract: OBJECTIVE
  Since the initial development of silicone hydrogels, many modifications to the bulk and surface properties of the lenses have been undertaken to improve the wettability and comfort of the lenses. Recently, manufacturers have incorporated various "wetting agents" or surface-active agents into the blister packaging solutions (BPSs) of the lenses to improve initial comfort of the lens on eye. The purpose of this study was to measure and compare the pH, surface tension (ST), viscosity, and osmolality of BPSs for a variety of silicone hydrogel and polyHEMA-based hydrogel lenses. In addition, two saline solutions were tested for comparison purposes.
  
  
  METHODS
  The pH, osmolality, ST, and viscosity were measured for the BPSs for lotrafilcon B and lotrafilcon A and lotrafilcon B with a "modified BPS" (m-lotrafilcon A, m-lotrafilcon B) (CIBA Vision, Duluth, GA); balafilcon A (Bausch & Lomb, Rochester, NY); galyfilcon A, senofilcon A, and narafilcon A (Johnson & Johnson, Jacksonville, FL); and comfilcon A and enfilcon A (CooperVision, Pleasanton, CA) and BPSs from two conventional polyHEMA-based materials-etafilcon A (Johnson & Johnson) and omafilcon A (CooperVision). The two saline solutions tested were Unisol (Alcon, Fort Worth, TX) and Softwear Saline (CIBA Vision).
  
  
  RESULTS
  The pH results for the two saline solutions and all BPSs remained in the pH range of tears (6.6-7.8). The ST of the modified BPS was significantly lower (p < 0.01) than the original non-modified BPS. Viscosity measurements ranged between 0.90 and 1.00 cP for all BPSs and saline solutions, except for the modified BPS, which had significantly higher viscosities (p < 0.001). Osmolality measurements were not significantly different (p > 0.05) between BPSs made by the same manufacturer but were significantly different compared with BPSs made by different manufacturers (p < 0.05).
  
  
  CONCLUSIONS
  The incorporation of wetting agents and surfactants into BPSs does alter the physical properties of the BPSs, which may have clinical implications regarding initial in-eye comfort.
authors.affiliation: University of Waterloo, Ontario, Canada. klmenzie@uwaterloo.ca
authors.forename: Kara L
authors.initials: KL
authors.lastname: Menzies
authors.forename: Lyndon
authors.initials: L
authors.lastname: Jones
mesh_terms: D018639:Contact Lens Solutions / Q000737:chemistry / Q000494:pharmacology*; D003263:Contact Lenses, Hydrophilic; D004349:Drug Packaging; D006801:Humans; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D009994:Osmolar Concentration; D012828:Silicones; D012965:Sodium Chloride / Q000494:pharmacology; D013500:Surface Tension / Q000187:drug effects; D013501:Surface-Active Agents / Q000494:pharmacology*; D014783:Viscosity / Q000187:drug effects; D014906:Wetting Agents / Q000494:pharmacology*
chemical_list: D018639:Contact Lens Solutions; D012828:Silicones; D013501:Surface-Active Agents; D014906:Wetting Agents; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D012965:Sodium Chloride