title: Topographical thickness of the epithelium and total cornea after hydrogel and PMMA contact lens wear with eye closure.
abstract: OBJECTIVE
  To determine changes in topographical thickness of the epithelium and total cornea after hydrogel (2-hydroxyethyl methacrylate; HEMA or soft lens) and PMMA rigid contact lens wear with eyes closed, as measured by optical coherence tomography (OCT).
  
  
  METHODS
  Epithelial and total corneal thickness in 18 neophyte eyes was measured with OCT at intervals of 10 degrees across a 10-mm zone of the horizontal meridian of the cornea, before and after 3 hours of soft and rigid contact lens wear with the eye closed. These measurements were repeated 20 minutes after removal of the lenses.
  
  
  RESULTS
  Lens type, time, and location were found to be significant main influences (P < 0.0001) on corneal swelling in patched eyes, by three-way ANOVA, and there was a significant three-way interaction among lens type, time, and location (F((16,272)) = 1.78, P = 0.033). However, there was no significant main effect and interaction of epithelial thickness (F((16, 272)) = 0.33, P = 0.99). Immediately after removal of the lenses, total corneal thickness in the horizontal meridian was significantly greater with both soft and PMMA lenses (P < 0.001) at each location with each lens, compared with the baseline measurements. With both lenses, the increase in actual thickness and percentage of corneal swelling at the center was greater than at each peripheral point (excluding the first 10 degrees points; P < 0.005). HEMA lenses caused greater corneal swelling than the PMMA lenses at each location immediately after removal of the lenses (P < 0.005).
  
  
  CONCLUSIONS
  This study shows that corneal swelling is dependent on lens type and corneal location when eyes are closed, but epithelial thickness across the horizontal corneal meridian does not change during lens wear with eyes closed. OCT is an efficient method of measuring topographical corneal and epithelial thickness in response to contact lens wear.
authors.affiliation: Centre for Contact Lens Research, School of Optometry, University of Waterloo, Waterloo, Ontario, Canada.
authors.forename: Jianhua
authors.initials: J
authors.lastname: Wang
authors.forename: Desmond
authors.initials: D
authors.lastname: Fonn
authors.forename: Trefford L
authors.initials: TL
authors.lastname: Simpson
mesh_terms: D000328:Adult; D003261:Contact Lenses / Q000009:adverse effects*; D003315:Cornea / Q000473:pathology; D015715:Corneal Edema / Q000209:etiology / Q000473:pathology*; D019573:Epithelium, Corneal / Q000473:pathology*; D005260:Female; D006801:Humans; D007368:Interferometry; D008027:Light; D008297:Male; D008689:Methacrylates; D019904:Polymethyl Methacrylate; D014054:Tomography / Q000379:methods
chemical_list: D008689:Methacrylates; C005044:hydroxyethyl methacrylate; D019904:Polymethyl Methacrylate