title: Contact lenses wettability in vitro: effect of surface-active ingredients.
abstract: OBJECTIVE
  To investigate the release of surface-active agents (surfactants) from unworn soft contact lenses (SCLs) and their influence on the lens surface wettability in vitro.
  
  
  METHODS
  Surface tension (ST) of blister pack solutions was measured by pendant-drop technique. STs at the air-aqueous interface and contact angles (CAs) of four conventional and seven silicone hydrogel SCLs were evaluated in a dynamic-cycling regime using a modified captive-bubble tensiometer-goniometer. Measurements were performed immediately after removal from blister packs, and after soaking in a glass vial filled with a surfactant-free solution, which was replaced daily for 1 week. Lens surface wettability was expressed as adhesion energy according to Young equation.
  
  
  RESULTS
  STs of all blister pack solutions were lower than the reference ST of pure water (72.5 mN/m), indicating the presence of surfactants. When lenses were depleted of surfactants by soaking, the STs for all studied lenses and advancing CAs of selected lenses increased (p < 0.001). Receding CAs of all studied lenses were 12 degrees +/- 5 degrees and were not affected by the presence of surfactants. For most of the conventional lenses, the surface wettability was largely dependent on surfactants, and reduced significantly after surfactant depletion. In contrast, most silicone hydrogel lenses exhibited stable and self-sustained surface wettability in vitro.
  
  
  CONCLUSIONS
  The manufacturer-added surfactants affected wetting properties of all studied SCLs, although to different degrees.
authors.affiliation: Clinical Research Center (CRC), School of Optometry, University of California, Berkeley, Berkeley, California 94720-2020, USA. mlin@berkeley.edu
authors.forename: Meng C
authors.initials: MC
authors.lastname: Lin
authors.forename: Tatyana F
authors.initials: TF
authors.lastname: Svitova
mesh_terms: D000388:Air; D003261:Contact Lenses; D003263:Contact Lenses, Hydrophilic; D003624:Darkness; D004867:Equipment Design; D005740:Gases; D021621:Imaging, Three-Dimensional; D008027:Light; D013499:Surface Properties; D013500:Surface Tension; D013501:Surface-Active Agents; D017155:Wettability
chemical_list: D005740:Gases; D013501:Surface-Active Agents
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