METHODS:A self-controlled study was used. Eighty four young myopic subjects(156 eyes)aged 12.60±2.03 years in which there were forty males and forty-four females with spherical equivalent(SE)-3.65±0.79D were recruited in the study from March 1^st 2013 to May 30^th 2015. Based on diopters, the subjects were divided into group A(-0.75～-2.00D), group B(-2.25～-4.00D)and group C(-4.25～-6.00D). All the lenses were worn every night over 8 hours. Uncorrected visual acuity(UCVA),subjective refraction,best corrected visual acuity(BCVA), contrast sensitivity function were examined before,1,6,12mo after the initiation of orthokeratology. The database was analyzed by SPSS17.0 using one-way ANOVA.

RESULT:1)Comparison between risual acuity and SE: The UCVA improved significantly and SE decreased after wearing orthokeratology lens 1,6,12mo in 3 groups, showing significant decline in comparison with that before orthokeratology(P<0.05). There was no significant change among 1,6,12mo after wearing orthokeratology(P>0.05). There was no significant change in BCVA(P>0.05). 2)Comparison on contrast sensitivity function: Contrast sensitivity function at all spatial frequencies in 3 groups 1,6,12mo after wearing lenses compared with those before wearing: There was no change before and after wearing at the low spatial frequency(3c/d)and the high spatial frequency(18c/d), but slight increases in group A and group B in the spatial frequency(6c/d, 12c/d)after wearing lenses. There were slight decreases in group C at all spatial frequencies after wearing.But there was no statistical significance between before and after wearing in all three groups(P>0.05).

CONCLUSION:Overnight orthokeratology can improve UCVA and has no obvious effect on the overall visual quality. It deserves to be applied and spreaded in clinical practice.