title: Consequences of wear interruption for discomfort with contact lenses.
abstract: OBJECTIVE
  To establish whether increased end-of-day discomfort during soft contact lens wear is associated with short-term changes occurring to the lens itself.
  
  
  METHODS
  Twenty-seven subjects wore hydrogel lenses (Focus Dailies; Alcon) bilaterally for 10 hours on two separate days. Comfort was reported using 1-100 numerical rating scales (1 = intolerable discomfort, 100 = lens cannot be felt). Day 1 ratings were taken before lens insertion and at 0.05, 5, and 10 hours post-insertion. Day 2 ratings occurred at similar times, but lenses were removed after the 5-hour assessment and either reinserted (n = 14) or newly replaced (n = 12). An additional rating was taken 5 minutes after re-insertion. Wear then continued to the 10-hour point. In a separate study, 24 different subjects repeated these procedures using a silicone hydrogel lens (AirOptix Aqua; Alcon) with wear taking place on 3 days to permit lens replacement to be with existing as well as new lenses in all subjects.
  
  
  RESULTS
  For hydrogel lenses, comfort scores (mean ± 95% CI) reported after 10 hours were 79.4 ± 8.3 when lenses were worn un-replaced, compared with 73.2 ± 9.2 for replacement with the existing lens. When replacement was with a brand new lens, the corresponding values were 72.9 ± 10.9 (un-replaced) versus 69.2 ± 12.8 (new lens replacement). For silicone hydrogel lenses, 10-hour comfort was 90.3 ± 3.2 (un-replaced) versus 92.2 ± 2.9 (replacement with existing lens) versus 90.0 ± 3.3 (replacement with new lens). Differences between replacement conditions were not significant in any case (analysis of variance, p > 0.05).
  
  
  CONCLUSIONS
  Final comfort was not influenced by replacing lenses midway through the wearing period. Comfort decrements experienced by users of these daily contact lenses towards the later part of the wearing period are not caused by changes occurring to the lenses on this time scale. Possible alternative etiological factors include a fatigue-like response in one or more ocular tissues or stimulation of ocular surface nociceptors induced by the presence of the contact lens.
authors.affiliation: *PhD, BScOptom, FAAO †MOptom ‡BOptom §PhD, BOptom Brien Holden Vision Institute (EBP, DTi), Sydney; School of Optometry and Vision Science (EBP, DTo, JW, EC, JC, BG), University of New South Wales, Sydney; and Vision CRC (EBP), Sydney, New South Wales, Australia.
authors.forename: Eric B
authors.initials: EB
authors.lastname: Papas
authors.forename: Daniel
authors.initials: D
authors.lastname: Tilia
authors.forename: Daniel
authors.initials: D
authors.lastname: Tomlinson
authors.forename: Josh
authors.initials: J
authors.lastname: Williams
authors.forename: Eddy
authors.initials: E
authors.lastname: Chan
authors.forename: Jason
authors.initials: J
authors.lastname: Chan
authors.forename: Blanka
authors.initials: B
authors.lastname: Golebiowski
mesh_terms: D000293:Adolescent; D000328:Adult; D003263:Contact Lenses, Hydrophilic / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D008297:Male; D008875:Middle Aged; D017060:Patient Satisfaction / Q000706:statistics & numerical data*; D014785:Vision, Ocular / Q000502:physiology; D055815:Young Adult
chemical_list: D020136:Hydrogel, Polyethylene Glycol Dimethacrylate