Corneal power change is predictive of myopia progression in orthokeratology.
OBJECTIVE
This study aims to investigate the relationship between corneal refractive power change along three axes (nasal, temporal, and inferior) after orthokeratology (OK) treatment and 2-year axial growth in children.


METHODS
Thirty-two Chinese children aged from 9 to 14 were fitted with OK. When corneal reshaping process following OK treatment was completed and stabilized, the 3-month topographic outputs were taken as the post-OK data. Corneal refractive powers along the nasal, temporal, and inferior axes were collected over an 8-mm-diameter ring in 1-mm steps using the sagittal power map. The maximum power change along each axis was selected and divided into two subcategories, level 1 and level 2, depending on whether the value was below or above the average. Axial length (AL) was measured every 6 months during a 24-month period. The relationship between the maximum power changes and 2-year axial elongation were analyzed.


RESULTS
Twenty-seven subjects completed the 24-month study. After OK treatment, statistically significant steepening (p < 0.05) was observed at the nasal 2 mm and 3 mm; temporal 3 mm; and inferior 2 mm, 3 mm, and 4 mm locations compared with the apical center. AL increased significantly throughout the 24-month observation period (p < 0.001). Changes in corneal refractive power significantly affected axial elongation (nasal, p = 0.001; temporal, p = 0.011; inferior, p = 0.001). Two-year axial elongation in patients with larger corneal power changes (level 2) was reduced by 54% to 69% compared with those with smaller corneal power changes (level 1). Maximum power changes along the three axes were negatively correlated (p < 0.05) with 2-year axial growth.


CONCLUSIONS
Subjects with larger magnitude of corneal relative peripheral power change along specific axes after OK treatment experienced slower axial elongation by the end of 24 months. This effect might be mediated by the induction of greater amount of relative myopic defocus on the peripheral retina. Our study lends weight to potential OK lens designs for myopia control in children.
*MD †MD, PhD ‡MD, MSc Department of Ophthalmology and Vision Science, Eye & ENT Hospital, Fudan University, Shanghai, China.
Yuanyuan
Y
Zhong
Zhi
Z
Chen
Feng
F
Xue
Jiaqi
J
Zhou
Lingling
L
Niu
Xingtao
X
Zhou
D000293:Adolescent; D058452:Axial Length, Eye / Q000473:pathology; D002648:Child; D003261:Contact Lenses; D003315:Cornea / Q000503:physiopathology*; D019781:Corneal Topography; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D009216:Myopia / Q000503:physiopathology* / Q000628:therapy*; D054158:Orthokeratologic Procedures; D011446:Prospective Studies; D017755:Prosthesis Fitting; D012029:Refraction, Ocular / Q000502:physiology