Authors: Wei Shifei, Li Shiming, Sun Yunyun, Kang Mengtian, Meng Bo, Ran Anran, Yan Ran, Bai Yawen, Zhuo Chen, Wang Ningli
It has been reported that orthokeratology has the effects of slowing down myopia progression and axial elongation.However, the affecting mechanism of orthokeratology wearing on ocular peripheral refraction is still not elucidated.
This study was to observe and compare the changes of ocular peripheral refraction and relative peripheral refraction (RPR) in low to moderate myopic eyes of children after wearing orthokeratology lens and spectacles for 6 months.
A randomized controlled clinical trial was carried out after approval of Ethic Committee of Beijing Tongren Hospital and informed consent of guardians of the children.One hundred myopic children aged (11.0±1.9) years were recruited in Beijing Tongren Hospital from June 2014 to January 2015, with the diopter of -0.50 to -6.00 D. The subjects were randomized into orthokeratology group and spectacles group by the process PLAN PROC of software SAS 9.1.3, 50 for each group.The subjects in the orthokeratology group wore orthokeratology lens for 6 months and those in the spectacles group wore spectacles for the same period.An infrared open-field autorefractor was employed to measure the refraction at central 0°, temporal 15°, temporal 30°, nasal 15°and nasal 30° radial lines before and after wearing lens for the assessment and comparison of the changes of peripheral refraction and RPR.
There was no significant difference in spherical equivalent between the orthokeratology group and the spectacles group before wearing lens ([-3.35±1.31]D versus [-3.01±1.15]D, P=0.20). The peripheral refraction values in the orthokeratology group were (-2.28±1.60), (-3.28±1.41), (-3.40±1.23), (-3.38±1.12) and (-2.09±1.29)D at nasal 15°and nasal 30°, central, temporal 15° and temporal 30°radial lines before wearing lens, and reduced by (0.29±1.67), (0.85±1.66), (0.92±1.76) and (0.66±1.66)D at nasal 30°, nasal 15°, central and temporal 15° after wearing lens, respectively, with significant differences at nasal 15°, central and temporal 15°(all at P<0.05). The peripheral refraction values in the spectacles group were (-1.88±1.30), (-2.66±1.18), (-2.89±1.27) and (-1.94±1.31)D at nasal 15°, nasal 30°, temporal 15° and temporal 30°, radial lines before wearing lens and increased by (-0.25±0.80), (-0.43±0.67), (-0.32±0.64) and (-0.22±0.75)D after wearing lens, respectively, with significant differences between before and after wearing lens (all at P<0.05). The RPR shifted from hyperopia defocus to myopia defocus before and after wearing lens in temporal 15° and 30° radial lines in the orthokeratology group, and at various radial lines in the spectacles group, the RPR showed gradually worsening of hyperopia defocus.
Long-term wearing of orthokeratology results in a hyperopia shifting in myopic children by exposing the peripheral retina towards relative myopia defocus, whereas wearing spectacles leads to a relative hyperopia defocus on retina.Thus, orthokeratology may slow down the myopia progression.