title: A pilot study on the corneal biomechanical changes in short-term orthokeratology.
abstract: OBJECTIVE
  To investigate the biomechanical changes in the cornea, in terms of corneal hysteresis (CH) and corneal resistance factor (CRF), with short-term orthokeratology (ortho-k) treatment, using the Ocular Response Analyser (ORA; Reichert Ophthalmic Instruments, Buffalo, NY, USA).
  
  
  METHODS
  Twenty young myopes wore ortho-k lenses in four different sessions: 15, 30, 60 min and overnight respectively. Except for the overnight session which was always the final trial, those sessions were randomly assigned with a 1-week washout period in between. CH and CRF were measured using the ORA and results were compared between the baseline and after each wearing session.
  
  
  RESULTS
  The mean baseline CH and CRF were 11.1 +/- 1.0 mmHg and 10.7 +/- 1.3 mmHg, respectively. There was no significant change in CH throughout the study, while a decreasing trend of CRF was shown. Paired t-test with Bonferroni correction found a significantly reduced CRF of 10.1 mmHg after overnight wear.
  
  
  CONCLUSIONS
  Short-term ortho-k treatment was shown to alter some corneal biomechanical properties. CRF was shown to decrease with increasing duration of lens wear. Further study is warranted to investigate the long term effect on corneal biomechanics from ortho-k treatment.
authors.affiliation: School of Optometry, The Hong Kong Polytechnic University, Hung Hom, Hong Kong. 05901208r@polyu.edu.hk
authors.forename: Davie
authors.initials: D
authors.lastname: Chen
authors.forename: Andrew K C
authors.initials: AK
authors.lastname: Lam
authors.forename: Pauline
authors.initials: P
authors.lastname: Cho
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D003261:Contact Lenses; D003315:Cornea / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D009216:Myopia / Q000628:therapy*; D054158:Orthokeratologic Procedures; D010865:Pilot Projects; D012029:Refraction, Ocular; D013997:Time Factors; D016896:Treatment Outcome; D055815:Young Adult