title: Comparative study of silicone-hydrogel contact lenses surfaces before and after wear using atomic force microscopy.
abstract: OBJECTIVE
  The aim of this study was to analyze surface changes of three silicone-hydrogel contact lenses after daily wear. The lenses used in this study were balafilcon A, lotrafilcon B (both surface-treated), and galyfilcon A (non surface-treated).
  
  
  METHODS
  To understand how and where proteins, lipids, and other contaminants change contact lenses, surface roughness was assessed through Atomic Force Microscopy Tapping Mode. Roughness parameters were Mean Surface roughness (R(a)), Mean-square-roughness (R(q)), and Maximum roughness (R(max)). The surface topography of unworn and worn lenses was also mapped in great detail.
  
  
  RESULTS
  Contact lenses roughness parameters exhibited different values before and after wear and the surface appearance also changed. After wear, balafilcon A and galyfilcon A showed a significant increase on surface roughness parameters, being this increase more accentuated to galyfilcon A. In lotrafilcon B materials no significant changes were observed with wear.
  
  
  CONCLUSIONS
  The present study suggests that surface treatment of silicone-hydrogel contact lenses can play a role in the prevention of a significant increase in roughness, and contribute to the better clinical tolerance of these lenses.
authors.affiliation: Department of Physics (Optometry), School of Sciences, University of Minho, Portugal. mlira@fisica.uminho.pt
authors.forename: M
authors.initials: M
authors.lastname: Lira
authors.forename: L
authors.initials: L
authors.lastname: Santos
authors.forename: J
authors.initials: J
authors.lastname: Azeredo
authors.forename: E
authors.initials: E
authors.lastname: Yebra-Pimentel
authors.forename: M Elisabete C D Real
authors.initials: ME
authors.lastname: Oliveira
mesh_terms: D003263:Contact Lenses, Hydrophilic; D005260:Female; D006801:Humans; D020100:Hydrogels; D008297:Male; D008422:Materials Testing / Q000379:methods; D018625:Microscopy, Atomic Force / Q000379:methods; D012828:Silicones; D013499:Surface Properties
chemical_list: D020100:Hydrogels; D012828:Silicones; C523195:balafilcon A; C524582:lotrafilcon B