The longitudinal orthokeratology research in children (LORIC) in Hong Kong: A pilot study on refractive changes and myopic control

Hie Hua Wong, Sin Wan Cheung, Marion Edwards

Research output: Journal article publicationJournal articleAcademic researchpeer-review

338 Citations (Scopus)


Purpose: Myopia is a common ocular disorder, and progression of myopia in children is of increasing concern. Modern overnight orthokeratology (ortho-k) is effective for myopic reduction and has been claimed to be effective in slowing the progression of myopia (myopic control) in children, although scientific evidence for this has been lacking. This 2 year pilot study was conducted to determine whether ortho-k can effectively reduce and control myopia in children. Methods: We monitored the growth of axial length (AL) and vitreous chamber depth (VCD) in 35 children (7-12 years of age), undergoing ortho-k treatment and compared the rates of change with 35 children wearing single-vision spectacles from an earlier study (control). For the ortho-k subjects, we also determined the changes in corneal curvature and the relationships with changes of refractive errors, AL and VCD. Results: The baseline spherical equivalent refractive errors (SER), the AL, and VCD of the ortho-k and control subjects were not statistically different. All the ortho-k subjects found post-ortho-k unaided vision acceptable in the daytime. The residual SER at the end of the study was -0.18 ± 0.69 D (dioptre) and the reduction (less myopic) in SER was 2.09 ± 1.34 D (all values are mean ± SD). At the end of 24 months, the increases in AL were 0.29 ± 0.27 mm and 0.54 ± 0.27 mm for the ortho-k and control groups, respectively (unpaired t test; p = 0.012); the increases in VCD were 0.23 ± 0.25 mm and 0.48 ± 0.26 mm for the ortho-k and control groups, respectively (p = 0.005). There was significant initial corneal flattening in the ortho-k group but no significant relationships were found between changes in corneal power and changes in AL and VCD. Conclusion: Ortho-k can have both a corrective and preventive/control effect in childhood myopia. However, there are substantial variations in changes in eye length among children and there is no way to predict the effect for individual subjects.
Original languageEnglish
Pages (from-to)71-80
Number of pages10
JournalCurrent Eye Research
Issue number1
Publication statusPublished - 1 Jan 2005


  • Axial length
  • Eye elongation
  • Myopia progression
  • Myopia reduction
  • Orthokeratology

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems
  • Cellular and Molecular Neuroscience

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