title: Vertical and horizontal thickness profiles of the corneal epithelium and Bowman's layer after orthokeratology.
abstract: OBJECTIVE
  To investigate thickness profile changes of the corneal epithelium and Bowman's layer at the vertical and horizontal meridians with overnight myopia orthokeratology (OK) lenses.
  
  
  METHODS
  Twenty subjects (age range: 19-33 years) wore reverse-geometry rigid gas-permeable OK lenses in both eyes for 30 days. Before lens wear and after 1, 7, and 30 days of overnight lens wear, evaluation of lens fitting, visual acuity examination, corneal topography, and ultra-high resolution optical coherence tomography (UHR-OCT) were performed. The central, midperipheral, and peripheral cornea were imaged in both the horizontal and vertical meridians. Custom software was produced to acquire the thickness profiles of the epithelium and Bowman's layer.
  
  
  RESULTS
  Unaided visual acuity and refraction were improved significantly after OK lens wear. The central corneal epithelium thinned in the horizontal and vertical meridians after one night of lens wear (P < 0.05). In the horizontal meridian, the epithelium thickened at the temporal and nasal midperipheries (P < 0.05), while the superior midperipheral epithelium thinned in the vertical meridian. There were no changes in the thickness profile of Bowman's layer during the study period.
  
  
  CONCLUSIONS
  Overnight wear of OK lenses caused the central corneal epithelium to thin in both the vertical and horizontal meridians, while the midperipheral nasal and temporal epithelium became thicker and the superior midperipheral epithelium became thinner. The thickness of the central or midperipheral Bowman's layer in either meridian did not change. Improved vision acuity after overnight OK lens wear can be attributed to changes in the corneal epithelium and not Bowman's layer.
authors.affiliation: School of Ophthalmology and Optometry, Wenzhou Medical College, Wenzhou, Zhejiang, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Lian
authors.forename: Meixiao
authors.initials: M
authors.lastname: Shen
authors.forename: Jun
authors.initials: J
authors.lastname: Jiang
authors.forename: Xinjie
authors.initials: X
authors.lastname: Mao
authors.forename: Ping
authors.initials: P
authors.lastname: Lu
authors.forename: Dexi
authors.initials: D
authors.lastname: Zhu
authors.forename: Qi
authors.initials: Q
authors.lastname: Chen
authors.forename: Jianhua
authors.initials: J
authors.lastname: Wang
authors.forename: Fan
authors.initials: F
authors.lastname: Lu
mesh_terms: D000328:Adult; D050541:Bowman Membrane / Q000473:pathology* / Q000601:surgery; D003261:Contact Lenses; D019781:Corneal Topography; D019573:Epithelium, Corneal / Q000473:pathology* / Q000601:surgery; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D009216:Myopia / Q000473:pathology / Q000601:surgery*; D054158:Orthokeratologic Procedures; D011184:Postoperative Period; D041623:Tomography, Optical Coherence; D014792:Visual Acuity; D055815:Young Adult