title: High myopia-partial reduction ortho-k: a 2-year randomized study.
abstract: OBJECTIVE
  To investigate if the combination of partial reduction (PR) orthokeratology (ortho-k) and spectacles for residual refractive errors in the daytime was effective to slow myopic progression in high myopic children.
  
  
  METHODS
  High myopic children (aged 8 to 11 years) with spherical equivalent refraction at least -5.75 diopters (D) and myopia -5.00 D or more myopic were recruited and randomly assigned into PR ortho-k and control groups. Subjects in the PR ortho-k group were fitted with custom made four-zone ortho-k lenses with target reduction of 4.00 D for both eyes, and the residual refractive errors were corrected with single-vision spectacles for clear vision in the daytime. Control subjects were fully corrected with single-vision spectacles. Axial length of each eye of all subjects was measured with the IOLMaster at 6-month intervals by a masked examiner. This study was registered at www.clinicaltrial.gov with the identifier NCT00977236.
  
  
  RESULTS
  Fifty-two subjects were recruited and randomized to the PR ortho-k and control groups. Twelve PR ortho-k and 16 control subjects completed the study. Compared with the residual refractive errors at the 1-month visit (after stabilization of ortho-k treatment), the median increase in noncycloplegic residual myopia at the 24-month visit was 0.13 D. In the control group, the median increase in myopia was 1.00 D at the end of the study. The mean ± SD increases in axial length were 0.19 ± 0.21 mm in the PR ortho-k group and 0.51 ± 0.32 mm in the control group (95% confidence interval, -0.55 to -0.12; unpaired t test, p = 0.005).
  
  
  CONCLUSIONS
  This single-masked randomized study showed that PR ortho-k effectively slowed myopic progression in high myopes. Axial length elongation was 63% slower in PR ortho-k-treated children compared with children wearing spectacles.
authors: School of Optometry, The Hong Kong Polytechnic University, Hong Kong SAR, China. jessie@eyecare.com.hk
authors: Jessie
authors: J
authors: Charm
authors: Pauline
authors: P
authors: Cho
mesh_terms: D058452:Axial Length, Eye; D002648:Child; D019781:Corneal Topography; D018450:Disease Progression; D005139:Eyeglasses; D005260:Female; D006801:Humans; D008297:Male; D047728:Myopia, Degenerative / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D054158:Orthokeratologic Procedures; D012029:Refraction, Ocular / Q000502:physiology; D016037:Single-Blind Method; D016896:Treatment Outcome