RESUMO
[Objective] This prospective study was conducted to assess the influence of overnight orthokeratology (OK) on low,middle and high myopia in southern Chinese teenagers.[Methods] Fifty-four subjects (107 eyes,age 11.65 ± 2.44 years,mean±SD)who matched the inclusion criteria for OK were enrolled in the study.The subjects were divided into three groups according to the different refraction baseline (low myopia group:0.75 ～ 3.00 D,51 eyes;middle myopia group:3.25 ～ 5.00 D,36 eyes;high myopia group:5.25 ～ 9.00 D,20 eyes).Refraction,central corneal thickness,corneal keratometry,anterior chamber depth and axial length (AL) were measured at baseline and after 1 years using ocular biometry.The changes were evaluated and compared among the groups.Results were analyzed by SPSS 17.0 software.[Results] Fifty-four subjects (total 107 eyes) completed the 1-year follow-up examinations.At baseline,the spherical equivalent refractive error (SER) was-2.15 D ± 0.63 D,-4.20 D ± 0.54 D,and-6.63 D ±1.18 D in three groups.The axial length was (24.50-± 0.66) mm,(25.16-± 0.65) mm,and (26.35 ± 0.87) mm in the three groups,respectively.There were no significant differences among the groups in initial central corneal thickness,anterior chamber depth,central,flat and steep kerotometry.The increase in axial length during the 1-year study period was (0.22 ± 0.27) mm,(0.09-± 0.22)mm and (0.02-± 0.22) mm in three groups,respectively,and the difference was significant between low myopia group and middle myopia group (P =0.04),low myopia group and high myopia group (P =0.008),whereas no significant difference was found between middle myopia group and high myopia group (P =0.35).Spherical equivalence decreased dramatically in three groups after one year (all P ＜ 0.0001).And the difference was significant between low myopia group and middle myopia group (P ＜ 0.0001),low myopia group and high myopia group (P ＜ 0.0001).Central,flat and steep kerotometry after one year became flatten in all group (all P ＜0.0001).There were no significant differences in the change of central corneal thickness,anterior chamber depth and corneal diameter.[Conclusions] OK lens is more effective in middle and high myopia control than in the low myopia control.The change in corneal keratometry may be one of the main factors influencing the OK treatment effect.