title: Ex vivo analysis of cholesterol deposition for commercially available silicone hydrogel contact lenses using a fluorometric enzymatic assay.
abstract: OBJECTIVE
  Lipid deposition on silicone hydrogel (SiHy) lenses, which are believed to be caused by their hydrophobic surface, can lead to discomfort, reduced vision, and inflammatory reactions. This study used a highly specific and sensitive fluorometric enzymatic assay for ex vivo cholesterol analysis of seven types of SiHy lenses: balafilcon A, comfilcon A, enfilcon A, enhanced-lotrafilcon A, enhanced-lotrafilcon B, galyfilcon A, and senofilcon A.
  
  
  METHODS
  Cholesterol sorption was assessed in 140 previously worn SiHy lenses from 8 clinical trials conducted in the United States and Australia between 2006 and 2008. Patients wore the lenses for 2 to 4 weeks. Unworn negative control lenses for each lens material were obtained directly from the manufacturer. Lipids were isolated from the lenses using a two-step chloroform: methanol extraction method, and total cholesterol was quantified using a fluorometric enzymatic assay. Nonparametric Mann Whitney statistical analysis was performed to determine the differences in total cholesterol sorption between lens-specific data sets.
  
  
  RESULTS
  Enhanced-lotrafilcon A and enhanced-lotrafilcon B contact lenses showed significantly lower median total cholesterol sorption (median±quartile, 0.30±0.2 μg/lens and 0.09±0.1 μg/lens, respectively) than all other types of lenses that were tested (P<0.0001). By contrast, enfilcon A (3.96±0.8 μg/lens) and galyfilcon A (3.75±1.1 μg/lens) showed the highest median total cholesterol sorption of all tested lenses.
  
  
  CONCLUSIONS
  Cholesterol deposition in SiHy contact lenses seems to be lens polymer dependent. Enhanced-lotrafilcon A and enhanced-lotrafilcon B both sorbed the lowest amount of cholesterol compared with the other five types of SiHy lenses that were tested in this study.
authors.affiliation: Vision Care Research, Alcon Laboratories, Johns Creek, GA.
authors.forename: Walter L
authors.initials: WL
authors.lastname: Nash
authors.forename: Manal M
authors.initials: MM
authors.lastname: Gabriel
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002784:Cholesterol / Q000032:analysis* / Q000737:chemistry; D003263:Contact Lenses, Hydrophilic; D005260:Female; D006801:Humans; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000737:chemistry; D050356:Lipid Metabolism; D008297:Male; D008875:Middle Aged; D012828:Silicones / Q000737:chemistry; D055815:Young Adult
chemical_list: D012828:Silicones; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D002784:Cholesterol