新型Scheimpflug眼前节全景仪评估近视患者角膜屈光力的重复性和准确性

摘要

目的 采用Sirius眼前节全景仪2种方法获得近视患者角膜屈光力,评估其重复性与准确性.方法 前瞻性研究.52例(52眼)接受LASIK术前检查的近视患者,平均年龄为(21.6±4.8)岁,平均等效球镜度为(-4.8±2.1)D;分别应用Keratron角膜地形图仪和Sirius眼前节全景仪测量角膜屈光力,每只眼连续测量3次.Keratron提供角膜模拟屈光力Km,Sirius提供2种角膜屈光力:角膜模拟屈光力Sim K和不同入瞳直径下光路追迹法获得的入瞳角膜屈光力(MPE).变异系数、Cronbach's Alpha系数及组内相关系数评估Sirius获得的角膜屈光力的重复性;采用重复测量方差分析比较Sirius获得的Sim K、MPE与Keratron获得的Km之间的差异;采用Pearson相关分析Sim K、MPE和Km之间的相关性,Bland-Altman图评估Sim K、MPE和Km之间的一致性.结果 Sim K、MPE3、MPE4、MPE4.5、MPE5、MPE6、MPE7、Km分别为(42.91±1.52)D、(42.25±1.50)D、(42.42±1.52)D、(42.52±1.52)D、(42.63±1.55)D、(42.87±1.57)D、(43.11±1.60)D、(42.99±1.50)D.Sirius测量的所有参数变异系数均小于1％,Cronbach's Alpha系数和组内相关系数均大于0.99.Sim K比Km平均小0.08 D,差异有统计学意义(t=4.11,P＜0.01).MPE3比Km平均小0.74 D,差异有统计学意义(t=32.00,P＜0.01).Pearson相关分析显示Sim K、MPE与Km均有密切的相关性(r均＞0.98,P＜0.01).Bland-Altman图显示Sim K与Km、MPE3与Km的95％一致性区间分别为(-0.35 D,0.19 D)、(-1.07 D,-0.41 D).结论 Sirius 2种方法获得的近视患者角膜屈光力具有很好的重复性.Sim K和Km具有很好的一致性,可以替代使用.光路追迹法获得的角膜屈光力明显低于Km,不能直接代入IOL计算公式.%Objective To assess the repeatability and accuracy of two instruments for measuring corneal refractive power in myopic eyes:the Scheimpflug-Placido topographer (Sirius) and the Keratron topographer.Methods Fifty-two eyes of 52 pre-LASIK myopic volunteers whose mean age was 21.6±4.8 years,with an average spherical equivalent of-4.8±2.t D,were enrolled in this prospective study.Corneal refractive power was measured by both the Keratron topographer and the Sirius Scheimpflug-Placido topographer.Keratron measures Km,which is simulated keratometry; Sirius provides two kinds of corneal refractive power:Sim K and mean pupil power (MPE) under different pupil sizes using ray tracing.Three consecutive measurements were obtained.The coefficient of variation and Cronbach's alpha and intraclass correlation coefficient (ICC) were used to assess the repeatability of the Sim K and MPE obtained by Sirius.The differences between Sim K,MPE and Km were analyzed by a repeated-measures analysis of variance.Pearson correlation and Bland-Altman analysis were used to evaluate the correlation and agreement between Sim K,MPE and Km.Results The results of Km,Sim K,MPE3,MPE4,MPE4.5,MPE5,MPE6 and MPE7 were 42.91±1.52 D,42.25±1.50 D,42.42±1.52 D,42.52±1.52 D,42.63±1.55 D,42.87±1.57 D,43.11±1.60 D and 42.99±1.50 D,respectively.The coefficients of variation were lower than 1％ for all parameters measured by Sirius.Cronbach's Alpha and ICC were both higher than 0.99.The Sim K averaged 0.08 D lower than Km with statistically significant differences (t=4.11,P＜0.01).The MPE3 average was 0.74 D smaller than Km with statistically significant differences (t=32.00,P＜0.01).Pearson analysis indicated excellent correlations (r＞0.98,P＜0.01).The 95％ limits of agreement between Sim K and Km,MPE3 and Km were (-0.35 D,0.19 D),(-1.07 D,-0.41 D).Conclusion In myopic eyes,simulated keratometry measured by Sirius was similar to Keratron.The instruments can be regarded as clinically interchangeable.However,mean pupil power using ray tracing cannot be factored directly into intraocular lens power calculations.