长扫描深度谱域OCT测量圆锥角膜患者全角膜厚度的重复性和再现性

Repeatability and reproducibility of mapping the entire corneal thickness of keratoconicpatients using long scan depth spectral domain OCT

目的探讨长扫描深度谱域OCT（UL-OCT）N4量圆锥角膜患者的全角膜三维厚度分布的重复性与再现性。方法前瞻性研究。选取圆锥角膜患者10例（10眼），使用自行搭建的UL-OCT获得角膜的横断面图像．采用以角膜顶点为中心进行均等放射状B型扫描获取i维图像。通过全自动分割算法获取10mm直径范围角膜厚度分布图，并将测量结果与Pentacam三维眼前节分析诊断系统进行对比。2个仪器的重复性与再现性通过重复性系数与再现性系数（CoR）、组内相关系数（ICC）和变异系数（CV）进行比较。2个仪器的一致性通过配对t检验和Bland-Ahman方法进行分析。结果对于圆锥角膜患者，UL-OCT测量值的重复性系数为3．43～4．31μm，再现性系数为3．58～8．10μm。重复性和再现性的组内相关系数分别为0．998和0．995以上。Pentacam测量值的重复性系数为8．63～14．30μm，再现性系数为14．59～19．17μm。重复性和再现性的组内相关系数分别为0．997和0．994以上。UL-OCT系统测量的角膜厚度在中央区、旁中央区、过渡区、周围区分别为（468．9±38．6）μm、（482．5±48．6）μm、（515．5±57．0）μm、（588．0±52．5）μm。Pentacam系统测量的各区角膜厚度分别为（500．9＋50．0）μm、（533．9＋49．7）μm、（587．9±60．6）μm、（635．3±62．0）μm。Bland-Altman分析角膜厚度测量结果显示，2种仪器测量结果差值的95％一致性界限在中央区、旁中央区、过渡区分别为-44．49～108．59μm、-7．47～110．23μm、-13．21～131．68μm。结论在测量圆锥角膜患者全角膜厚度时，与Pentacam系统相比，UL-OCT系统具有更好的重复性和再现性。UL-OCT系统与Pentacam系统得到的角膜厚度测量结果存在差异，因此2种仪器在临床应用时不可互换。

Objective To investigate the repeatability and reproducibility of mapping the entire corneal thickness of keratoconic patients using long scan depth spectral domain OCT （UL-OCT）. Methods Ten patients （10 eyes） with keratoconus were recruited for this prospective study. A custom-built UL-OCT system was used to obtain radial frames of corneal images. The 3D scan pattern consisted of equally located B-scans centered on the corneal vertex reflection. Corneal thickness maps were generated by a fully automated segmentation algorithm over a 10 mm diameter of the corneal region. Corneal thicknesses were measured in the central zone （0-2 mm）, pericentral zone （〉2-5 mm）, transitional zone （〉5-7mm） and peripheral zone （〉7-10 mm）. The results were compared with those obtained with a Pentacam. The intraobserver repeatability and interobsever reproducibility of the two systems were analyzed by a coefficient of repeatability （CoR）, coefficient of reproducibility （CoR）, intraclass correlation coefficient （ICC） and coefficient of variation （CV）. The differences between the two systems were analyzed by a paired t test and Bland-Ahman method. Results For keratoconus UL-OCT measurements, the coefficients of repeatability were less than 4.31μm and the coefficients of reproducibility were less than 8.10μm. The intraclass correlation coefficients of repeatability and reproducibility were more than 0.998 and 0.995. For the Pentacam topography of keratoconic patients, the coefficients of repeatability were less than 14.30μm and coefficients of reproducibility was less than 19.17μm. ICCs of repeatability and reproducibility were more than 0.997 and 0.994. The UL-OCT system measurements of corneal thickness in the central zone, pericentral zone, transitional zone and peripheral zone were 468.9±38.6μm, 482.5±48.6μm, 515.5±57.0μm, and 588.0±52.5μm, respectively. Pentacam system measurements of corneal thickness in the same zones were 500.9±50.0μm, 533.9±49.7μm, 587.9±60.6μm, and 635.3±62.0 μm, respectively. The Bland-Altman analysis showed that the 95% limits of agreement between the two instruments in the central zone, perieentral zone, transitional zone were -44.49 to 108.59μm, -7.47 to 110.23μm, and 13.21 to 131.68μm, respectively. Conclusion There were significant differences in thickness measurements between UL-OCT and Pentacam topography, which makes these two devices non-interchangeable in the clinic.