title: Ocular discomfort responses after short periods of contact lens wear.
abstract: OBJECTIVE
  To investigate if contact lens-related discomfort is a function of the time of day at which lenses are worn.
  
  
  METHODS
  This was a randomized, crossover, open-label clinical trial where subjective responses, with and without contact lenses, were assessed every 2 hours during five stages (A to E). Each stage began at the time when subjects would normally have inserted their contact lenses (T0). During stage A, no lenses were worn, whereas in stage B, lenses were worn continuously for 12 hours. In stages C to E, lenses were worn for only 4 hours. Contact lenses were inserted at T0 for stage C, but for stages D and E, lenses were not inserted until T0 + 4 and T0 + 8 hours, respectively. Mixed linear models were used for statistical analysis.
  
  
  RESULTS
  In the absence of contact lenses, ocular comfort and dryness remained reasonably constant throughout the observation period. Ocular comfort and dryness decreased during 12 hours of continuous lens wear and became significantly worse from the 8-hour time onward compared with insertion (p < 0.023). There were no significant differences in terms of ocular comfort and dryness between any of the 4-hour lens wear stages (p < 0.82). During each 4-hour stage, both comfort and dryness behaved in a similar fashion (p > 0.05) to the first 4 hours of continuous contact lens wear. Comparing the scores of each of these stages with the no-lens response at the corresponding time showed no significant differences for comfort (p > 0.23) or dryness (p > 0.37).
  
  
  CONCLUSIONS
  Short periods of wear can be experienced at any time of day without significant change in ocular discomfort and dryness. This suggests that subjective responses at the end of the day are determined by the length of time lenses are in contact with the eye, rather than the time of day at which lenses are worn.
authors.affiliation: *PhD, FAAO †MOptom, FAAO ‡OD, FAAO §PhD Brien Holden Vision Institute, Sydney, New South Wales, Australia (EP, DT, PLdlJ); Vision Cooperative Research Centre, Sydney, Australia (EP, PLdlJ); School of Optometry and Vision Science, University of New South Wales, Sydney, New South Wales, Australia (EP, PLdlJ); and CIBA Vision, Duluth, Georgia (JMc).
authors.forename: Eric
authors.initials: E
authors.lastname: Papas
authors.forename: Daniel
authors.initials: D
authors.lastname: Tilia
authors.forename: John
authors.initials: J
authors.lastname: McNally
authors.forename: Percy Lazon
authors.initials: PL
authors.lastname: de la Jara
mesh_terms: D000328:Adult; D001248:Asthenopia / Q000209:etiology* / Q000503:physiopathology; D003261:Contact Lenses / Q000706:statistics & numerical data*; D018592:Cross-Over Studies; D015352:Dry Eye Syndromes / Q000209:etiology* / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D017060:Patient Satisfaction; D011446:Prospective Studies; D013312:Stress, Physiological; D011795:Surveys and Questionnaires; D013997:Time Factors