title: Influence of day and night wear on surface properties of silicone hydrogel contact lenses and bacterial adhesion.
abstract: OBJECTIVE
  The aim of this study was to determine the effect of continuous wear on physicochemical surface properties of silicone hydrogel (S-H) lenses and their susceptibility to bacterial adhesion.
  
  
  METHODS
  In this study, volunteers wore 2 pairs of either "lotrafilcon A" or "balafilcon A" S-H contact lenses. The first pair was worn continuously for a week and the second pair for 4 weeks. One lens of each pair was used for surface characterization and the other one for bacterial adhesion experiments. Lens surfaces were characterized by examination of their wettability, roughness, elemental composition, and proteins attached to their surfaces. Adhesion of Staphylococcus aureus 835 and Pseudomonas aeruginosa #3 to a lens was studied using a parallel plate flow chamber.
  
  
  RESULTS
  Before use, the lotrafilcon A lens was rougher than the balafilcon A lens and had a lower water contact angle and a higher affinity for S. aureus 835. After wear, both lens types had similar water contact angles, whereas the differences in elemental surface composition decreased as well. S. aureus 835 adhered in higher numbers to worn balafilcon A lenses, whereas the opposite was seen for P. aeruginosa #3. The initial deposition rates of both bacterial strains to lotrafilcon A lenses decreased by wearing and were found to correlate significant (P < 0.001) with the surface roughness of worn lenses.
  
  
  CONCLUSIONS
  In this study, the differences in surface properties between 2 types of S-H lenses were found to change after 1 week of continuous wear. Generally, bacteria adhered in lower numbers and less tenaciously to worn lenses, except S. aureus 835, adhering in higher numbers to worn balafilcon A lenses.
authors.affiliation: Department of BioMedical Engineering, University Medical Center Groningen, and University of Groningen, Groningen, The Netherlands.
authors.forename: Pit B J
authors.initials: PB
authors.lastname: Vermeltfoort
authors.forename: Minie
authors.initials: M
authors.lastname: Rustema-Abbing
authors.forename: Joop
authors.initials: J
authors.lastname: de Vries
authors.forename: Gerda M
authors.initials: GM
authors.lastname: Bruinsma
authors.forename: Henk J
authors.initials: HJ
authors.lastname: Busscher
authors.forename: Matthijs L
authors.initials: ML
authors.lastname: van der Linden
authors.forename: Johanna M M
authors.initials: JM
authors.lastname: Hooymans
authors.forename: Henny C
authors.initials: HC
authors.lastname: van der Mei
mesh_terms: D001422:Bacterial Adhesion / Q000502:physiology*; D015169:Colony Count, Microbial; D003262:Contact Lenses, Extended-Wear / Q000382:microbiology*; D004577:Electron Probe Microanalysis; D004591:Electrophoresis, Polyacrylamide Gel; D005136:Eye Proteins / Q000378:metabolism; D006801:Humans; D020100:Hydrogels / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D011485:Protein Binding; D011550:Pseudomonas aeruginosa / Q000502:physiology*; D012828:Silicones / Q000737:chemistry*; D013211:Staphylococcus aureus / Q000502:physiology*; D013499:Surface Properties; D011795:Surveys and Questionnaires; D017155:Wettability
chemical_list: D005136:Eye Proteins; D020100:Hydrogels; D012828:Silicones