title: Effects of silicone hydrogel contact lens wear on ocular surface sensitivity to tactile, pneumatic mechanical, and chemical stimulation.
abstract: OBJECTIVE
  To determine the effects of silicone hydrogel lens wear and lens-solution interactions on ocular surface sensitivity.
  
  
  METHODS
  Forty-eight adapted lens wearers completed the study, which comprised two phases. Phase 1 included habitual lens wear, no lens wear (7 ± 3 days), and balafilcon A lenses (PV; PureVision; Bausch & Lomb, Rochester, NY) with a hydrogen peroxide-based regimen for 2 weeks; phase 2 included wear of PV with the use of a multipurpose solution containing either polyhexamethylene-biguanide (PHMB) or Polyquad/Aldox (Alcon Laboratories, Fort Worth, TX) preservative, each for 1 week, with a 2-week washout period between solutions. Tactile and pneumatic (mechanical and chemical) stimuli were delivered, and thresholds were determined by Cochet-Bonnet (Luneau Ophthalmologie, Chartres, France) and Belmonte (Cooperative Research Centre for Eye Research and Technology, Sydney, NSW, Australia) pneumatic esthesiometers, respectively. Corneal and conjunctival thresholds and staining scores were assessed at baseline, after 2 and 8 hours of lens wear on day 1 and at the end of each wearing cycle (2 hours).
  
  
  RESULTS
  In phase 1, compared to the no-lens baseline, corneal tactile thresholds increased at the 1-day, 8-hour and the 2-week visits (P < 0.05), whereas conjunctival mechanical thresholds decreased at the 1-day, 2-hour and the 2-week visits (P < 0.05). In phase 2, the chemical thresholds were lower with PHMB-preserved solution compared with the Polyquad/Aldox system at the 1-day, 2-hour and the 1-week visits (P < 0.05). Staining scores correlated inversely with conjunctival chemical thresholds (all P < 0.05).
  
  
  CONCLUSIONS
  Ocular surface sensitivity changed in adapted lens wearers, when lenses were refit after a no-lens interval and during lens wear with different care regimens. The corneal staining that was observed with certain lens-solution combinations was accompanied by sensory alteration of the ocular surface-that is, higher levels of staining correlated with increased conjunctival chemical sensitivity. (ClinicalTrials.gov number, NCT00455455.).
authors.affiliation: Centre for Contact Lens Research, School of Optometry, University of Waterloo, Waterloo, Ontario, Canada.
authors.forename: Ping
authors.initials: P
authors.lastname: Situ
authors.forename: Trefford L
authors.initials: TL
authors.lastname: Simpson
authors.forename: Lyndon W
authors.initials: LW
authors.lastname: Jones
authors.forename: Desmond
authors.initials: D
authors.lastname: Fonn
mesh_terms: D000221:Adaptation, Ocular / Q000502:physiology; D000293:Adolescent; D000328:Adult; D000388:Air; D002245:Carbon Dioxide; D003228:Conjunctiva / Q000502:physiology*; D018639:Contact Lens Solutions; D003263:Contact Lenses, Hydrophilic; D003315:Cornea / Q000502:physiology*; D018592:Cross-Over Studies; D005260:Female; D006801:Humans; D020100:Hydrogels; D006941:Hyperesthesia / Q000503:physiopathology*; D008297:Male; D055595:Mechanical Phenomena; D008875:Middle Aged; D011310:Preservatives, Pharmaceutical; D017755:Prosthesis Fitting; D011984:Sensory Receptor Cells / Q000502:physiology; D012828:Silicones; D016037:Single-Blind Method; D013268:Stimulation, Chemical; D055815:Young Adult
chemical_list: D018639:Contact Lens Solutions; D020100:Hydrogels; D011310:Preservatives, Pharmaceutical; D012828:Silicones; C523195:balafilcon A; D002245:Carbon Dioxide