AIM:To investigate the changes in anterior segment parameters by Sirius anterior system after orthokeratology and the possible mechanisms.

METHODS: Twenty-eight patients(56 eyes)with myopia in our hospital from August 2014 to October 2014 were included. Spherical equivalent were -3.83±1.19D. Data of central corneal thickness(CCT), anterior chamber depth(ACD), anterior corneal curvature(a-K)and posterior corneal curvature(p-K)were collected and analyzed at before, 1d, 1wk and 3mo after orthokeratology.

RESULTS: After orthokeratology, spherical equivalent of all eyes decreased to predicted level. There were no significant differences in CCT and p-K between different times(P>0.05). There were significant differences in a-K between different times except between 1wk and 3mo after orthokeratology(P<0.05). There were significant differences in ACD between before and 1wk after, between 1d and 3mo after, between 1wk and 3mo after orthokeratology(P<0.05). There were correlations between CCT before orthokeratology(CCTpre)and the change at 3mo after orthokeratology(CCTc-3mo), between ACD before orthokeratology(ACDpre)and the change at 1d after orthokeratology(ACDc-1d), between a-K before orthokeratology(a-Kpre)and the changes at 1d(a-Kc-1d), 1wk(a-Kc-1wk)and 3mo(a-Kc-3mo)after, respectively(all P<0.05). Multiple linear regression suggested that a-Kc-1d(P=0.016), a-Kc-1wk(P=0.047)were correlated with a-Kpre and axial, respectively. And there were correlations between a-Kpre and a-Kc-3mo(P=0.024), between ACDpre and ACDc-1d(P=0.036), between CCTpre and CCTc-3mo(P=0.012), respectively.

CONCLUSION: CCT, ACD and p-K has no significant changes after orthokeratology, while there is significant difference in a-K, which is considered one of the most key factor in orthokeratology. Sirius anterior system for examination before orthokeratology and postoperative assessment, non-invasive, reliable and has a good clinical value.