角膜塑形术对角膜表面形态及角膜像差的影响

Effect of overnight orthokeratology on corneal surface morphology and corneal aberrations

目的观察和分析角膜塑形术后角膜表面形态及角膜像差的变化，并评估角膜塑形偏心量对角膜像差的影响。方法前瞻性临床研究。对22例年龄为（24．4±2．2）岁的中低度近视[（-2．23±0．74）D1患者采用夜戴型角膜塑形镜矫治近视。分别在配戴角膜塑形镜前．戴镜后1周、1个月时用开视野红外验光仪（Grand Seiko 5500）测量中心近视度数：用Medmont E-300角膜地形图仪进行角膜地形检查，通过角膜地形图得到角膜塑形偏心数据（包括幅度和方向）、角膜曲率（K值），用Matlab软件将角膜地形图数据转化成角膜像差数据，只取右眼数据进行研究。数据分别采用配对t检验、独立样本￡检验、单因素方差分析、Pearson相关进行分析。结果配戴角膜塑形镜后眼近视度数即开始有效减低，角膜中心表面曲率也同时开始降低，两者1周之后都趋于稳定。戴镜第1周时的平均偏心量是（0．49±0．24）mm。与1个月时的偏心量差异无统计学意义；偏心方向主要在颞侧，其次是下方。戴镜后角膜表面的总高阶像差、三阶像差、四阶像差均方根值相对戴镜前增加，1周之后趋于稳定。角膜三阶像差变化量与偏心幅度呈正相关（r=0.492，P〈0．05）；四阶像差变化量与偏心的相关性无统计学意义；角膜三阶像差中的一级彗差变化量与偏心在幅度和方向上都呈正相关（r=0．546，P〈0．05；r=0．710，P〈0．05）。初始散光较大者的偏心量并不比散光较小者大，差异无统计学意义。结论角膜塑形术在1周之内即可有效降低近视度数、角膜曲率；角膜总高阶像差及三阶、四阶像差均增大．其中三阶像差中的一级彗差增加量与角膜塑形偏心相关。角膜塑形术后的偏心量不取决于初始的散光度数。

Objective To evaluate the changes of the corneal surface morphology and corneal aberrations undergoing overnight orthokeratology treatment and to assess the effect of the amount of deeentration on corneal aberrations. Methods This was a prospective clinical study. Twenty-two patients with low and moderate myopia [（-2.23±0.74）D] aged （24.4±2.2）years were included and fitted with Ortho-K contact lenses （CL）. The center refractive status was measured with an open field infrared refractometer （Grand Seiko 5500）; corneal topography and the amount of decentration （including the magnitude and the orientation） were measured with Medmont E-300 Corneal Topographer, corneal topography data were converted into aberrations data by a Matlab software. The measurements were taken in right eyes, at pre-wear, 7 days and 30 days after orthokeratology. Data were analyzed with a paired t test, an independent samples t test, an one-way ANOVA, or a Pearson correlation analysis. Results The myopia amount of all subjects were significantly reduced after Ortho-K CL wear within the first week. The reduction also happened in central corneal curvature. The average amount of deeentration of 1 week was （0.49±0.24）mm, no more significant changes thereafter. The direction of decentration was mainly in the temporal side, followed by the bottom side. Root mean square （RMS） of corneal total higher-order aberrations, third-order aberration, fourth-order aberration were significantly increased compared to before wear and the changes were stabilized after1 week. Corneal third-order aberrations variation correlated with decentration （r=0.492, P〈0.05）; corneal fourth-order aberration variation did not show significant correlation with decentration; the combined coma variation significantly correlated with both orientation and magnitude of decentration （r=0.546, P〈0.05; r=0.710, P〈O.05）. Initial higher astigmatism did not induce the greater amount of decentration. Conclusion Myopia amount reduction along with corresponding corneal curvature changes occurre mostly within 1 week after orthokeratogy; corneal total higher-order aberrations, third-order aberration and fourth-order aberration increase, the addition of coma relate to the deeentration after orthokeratology; the deeentration after orthokeratology do not relate to the initial astigmatism.