High Myopia partial reduction using orthokeratology (HM-PRO)

Abstract

PURPOSE: The High Myopia Partial Reduction Orthokeratology (HM-PRO) study was a 2-year, single-masked, randomized clinical study which assessed the clinical performance of partial reduction using orthokeratology (ortho-k) and myopic progression in high myopic children after two years of lens wear. METHODS: Children (8 to 11 years old) with spherical equivalent refraction 5.75D or above were recruited and randomly assigned into PR (partial reduction) ortho-k and control groups. PR ortho-k group used a custom made 4-zone ortho-k lenses (DreamLite, Procornea, The Netherlands) of target 4.00D to reduce the refractive errors. Residual refractive errors were corrected with a pair of glasses. Control subjects were fully corrected with single vision spectacles. Axial length (AL) was monitored with the IOLMaster during the treatment period. Complete ocular biometric data were collected at 6-month intervals. Analysis was performed on data from the right eye only. RESULTS: During the study, 79 children were screened, and 52 (66%) were eligible and enrolled. Half of the subjects were randomly assigned to PR ortho-k group and the other half to the control group. In PR ortho-k group, the median (range) myopic reduction and residual myopia were 3.75D (2.25D to 5.00D) and 2.75D (1.50D to 5.25D) respectively after 1-month lens wear. Residual refractive errors were corrected by a pair of spectacles and no significant difference was found in BCVA after stabilization of treatment at the 1-month visit. Pigmented arc was found in 32% of subjects after one month of lens wear. Observations of fluorescein staining of the cornea (less than Grade 2) were noted in some subjects at the 1-month visit. Twelve PR ortho-k and 16 control subjects completed this 2-year study. At the end of the study period, the median reduction in myopia was 4.50D (range: 2.75D to 6.25D) in the PR ortho-k group. Compared to the residual refractive errors at the 1-month visit (after lens stabilization), the median change in residual non-cycloplegic myopia at the 24-month visit was 0.13D (range: -0.75 to 1.00D). In the control group, the median increase in myopia was 1.00D (range: 0.50 to 2.50D). No significant change in astigmatism was observed in both groups. Corneal staining was observed in both groups of subjects at each visit but the frequency was generally higher in the PR ortho-k treated subjects At the end of the 2-year monitoring period, the mean±SD increases in AL were 0.19±0.21mm for the PR ortho-k group and 0.51±0.32mm for the control group (p=0.005). AL elongation was 63% slower in PR ortho-k treated children when compared to children wearing spectacles. CONCLUSIONS: This study showed that PR ortho-k with spectacles for correcting residual refractive errors is safe and can be offered to high myopic children who wish to undergo ortho-k treatment for myopic control. This mode of treatment can retard myopic progression in high myopic children.