title: A comparative study of biweekly disposable contact lenses: silicone hydrogel versus hydrogel.
abstract: BACKGROUND
  Our aim was to compare the clinical performance of a biweekly (second generation) silicone hydrogel lens and a biweekly hydrogel lens worn for daily wear modality.
  
  
  METHODS
  We used a double-masked study, in which non-presbyopic, asymptomatic and adapted soft lens wearers were recruited. Subjects wore a silicone hydrogel lens in one eye and a hydrogel lens in the other (lens types and eyes were randomly assigned) for one month. Lenses were replaced every two weeks. Contact lens fitting, pre-lens tear film thinning time, vision, corneal integrity and lens deposits were assessed before and every fortnight after delivery of new lenses. A questionnaire was used to compare the subjective performance of the two lens types.
  
  
  RESULTS
  Thirty of the 33 subjects completed the study. There were no significant differences in lens fitting (centration and movement), pre-lens tear film thinning time, vision or corneal integrity between the two lens types. Statistically, there was no significant difference in lens deposits between the two lens types but silicone hydrogel lenses tended to have more Grade 3 to 4 lipid deposits than hydrogel lenses. Subjects found no significant differences between the two lens types in terms of vision and comfort. Preference for silicone hydrogel lenses increased from 33 at the first after-care visit to 50 per cent at the second after-care visit.
  
  
  CONCLUSIONS
  This short-term study demonstrates that the performance of silicone hydrogel and hydrogel lenses is comparable but the former tends to build up more lipid deposits than the latter. We did not find better performance in terms of ocular integrity of silicone hydrogel lenses compared to the hydrogel lenses, probably because the subjects were adapted asymptomatic contact lens wearers before commencing the study. Contact lens wearers having hypoxia-related problems are likely to benefit from using silicone hydrogel lenses, as these lenses provide at least three times more oxygen than conventional hydrogel lenses.
authors.affiliation: School of Optometry, The Hong Kong Polytechnic University, Hong Kong SAR, China. sopeggy@polyu.edu.hk
authors.forename: Sin-Wan
authors.initials: SW
authors.lastname: Cheung
authors.forename: Pauline
authors.initials: P
authors.lastname: Cho
authors.forename: Ben
authors.initials: B
authors.lastname: Chan
authors.forename: Camus
authors.initials: C
authors.lastname: Choy
authors.forename: Vincent
authors.initials: V
authors.lastname: Ng
mesh_terms: D000328:Adult; D003263:Contact Lenses, Hydrophilic / Q000009:adverse effects; D004209:Disposable Equipment; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D066298:In Vitro Techniques; D008055:Lipids / Q000032:analysis; D008297:Male; D017060:Patient Satisfaction; D012828:Silicones; D013499:Surface Properties; D011795:Surveys and Questionnaires; D013997:Time Factors; D014785:Vision, Ocular
chemical_list: D008055:Lipids; D012828:Silicones; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate