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High MyopiaPartial Reduction Ortho-k: A 2-Year Randomized Study

Charm, Jessie*; Cho, Pauline

doi: 10.1097/OPX.0b013e318293657d
Original Articles

Purpose: 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 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.



School of Optometry, The Hong Kong Polytechnic University, Hong Kong SAR, China.

Jessie Charm School of Optometry The Hong Kong Polytechnic University Hong Kong SAR China e-mail:

© 2013 American Academy of Optometry