title: Effect of time and washing on the adhesion of Acanthamoeba to extended wear disposable hydrogel contact lenses.
abstract: OBJECTIVE
  This study was undertaken to determine the extent of adhesion of cysts and trophozoites of Acanthamoeba to worn disposable hydrogel lenses and to study the effect of time, lens material, and washing on the adhesion.
  
  
  METHODS
  Etafilcon A (58% water content) and Polymacon (38% water content) lenses worn on a 6 night extended wear basis and collected aseptically in PBS pH 7.2, were used for the study. Unworn lenses of the same materials were used as controls. Segments of lenses were incubated in Acanthamoeba suspension (cysts and trophozoites) and examined at 0, 5, and 24 hours, either washed or unwashed, for adherent Acanthamoeba. The amoebae adherent per square mm surface of the lens were enumerated. Levels of adhesion in various groups were compared using Wilcoxon sign rank test.
  
  
  RESULTS
  At 0 hours, unwashed worn Polymacon lenses showed significantly greater adherence than Etafilcon A lenses compared to the controls (P = 0.0469). However, there was no difference at 5 and 24 hours exposure time between the lenses. At 24 hours the adhesion of Acanthamoeba was greater for washed worn lenses of both types compared to washed lenses of controls (P = 0.002, 0.012).
  
  
  CONCLUSIONS
  Amoebae adhered with equal affinity to both types of lenses but adhered with greater affinity to worn lenses than unworn lenses. Adhesion of Acanthamoeba to worn disposable lenses may be a factor in the pathogenesis of Acanthamoeba keratitis in disposable lens wearers.
authors.affiliation: Bausch & Lomb Contact Lens Centre, Hyderabad, India.
authors.forename: L
authors.initials: L
authors.lastname: Ramachandran
authors.forename: D
authors.initials: D
authors.lastname: Janakiraman
authors.forename: S
authors.initials: S
authors.lastname: Sharma
authors.forename: G N
authors.initials: GN
authors.lastname: Rao
mesh_terms: D000048:Acanthamoeba / Q000378:metabolism*; D000268:Adhesiveness; D000293:Adolescent; D000328:Adult; D000818:Animals; D018441:Biofilms / Q000187:drug effects; D018639:Contact Lens Solutions / Q000494:pharmacology; D003262:Contact Lenses, Extended-Wear; D004209:Disposable Equipment; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D008297:Male; D011092:Polyethylene Glycols; D013997:Time Factors
chemical_list: D018639:Contact Lens Solutions; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D011092:Polyethylene Glycols