Purpose To evaluate the agreement of central corneal thickness (CCT) measurement between Scheimpflug imaging and ultrasound (U/S) pachymetry in keratoconic eyes, and investigate factors that affect the agreement. Methods This post hoc analysis within a prospective, observational non-randomised study preformed at the Kensington Eye Institute, Toronto, Ontario, Canada, included crosslinking candidates with progressive keratoconus (KC). Main outcome measures were the agreement of CCT measurement between Scheimpflug imaging (Pentacam Oculus, Wetzlar, Germany) and U/S pachymetry (PachPen 24–5100, Accutome Inc., Malvern, Pennsylvania, USA), and factors that affect the agreement. Results A total of 794 keratoconic eyes of 456 subjects with a mean age of 27.6±8.0 years (69.7% males and 49.6% right eyes) were included. Agreement between devices was moderate (intraclass correlation coefficient: 74.9%, Bland–Altman limits of agreement: −48.5 μm to +62.5 μm). In a multivariable analysis, cone decentration (p<0.001, coefficient +10.13 [+6.73 to +13.53 95% CIs]) and Kmax (p<0.001, coefficient +0.68 [+0.46 to +0.90 95% CIs]) were significantly associated (both clinically and statistically) with the level of agreement between the devices; the discrepancy in CCT between the devices increased on average by 10.13 μm for every mm of cone decentration, and by 6.8 μm for every 10D of Kmax. Age, corneal astigmatism and spherical equivalent were statistically but not clinically significant factors affecting agreement. Conclusion The agreement of CCT measurement between Scheimpflug imaging and U/S pachymetry in KC was moderate. To ensure the safety of crosslinking in keratoconic corneas, Scheimpflug and U/S CCT measurements should not be used interchangeably, especially in steep corneas and corneas with decentred cones.

中文翻译：

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影响圆锥角膜中央角膜厚度测量一致性的因素

目的 评价 Scheimpflug 成像和超声 (U/S) 角膜厚度测量在圆锥角膜中的中央角膜厚度 (CCT) 测量的一致性，并调查影响一致性的因素。方法 这项在加拿大安大略省多伦多肯辛顿眼科研究所进行的前瞻性、观察性非随机研究中的事后分析包括与进行性圆锥角膜 (KC) 交联的候选人。主要结果测量是 Scheimpflug 成像（Pentacam Oculus，Wetzlar，德国）和 U/S 厚度测量法（PachPen 24-5100，Accutome Inc.，Malvern，Pennsylvania，USA）之间 CCT 测量的一致性，以及影响一致性的因素。结果共纳入456名受试者的794只圆锥角膜，平均年龄为27.6±8.0岁（69.7%为男性，49.6%为右眼）。设备之间的一致性适中（组内相关系数：74.9%，Bland-Altman 一致性限制：-48.5 μm 至 +62.5 μm）。在多变量分析中，锥体偏心（p<0.001，系数 +10.13 [+6.73 至 +13.53 95% CI]）和 Kmax（p<0.001，系数 +0.68 [+0.46 至 +0.90 95% CI]）显着相关（临床和统计学）设备之间的一致性水平；设备之间的 CCT 差异平均每增加 1 mm 锥体偏心增加 10.13 μm，每 10D Kmax 增加 6.8 μm。年龄、角膜散光和等效球镜具有统计学意义，但不是影响一致性的临床显着因素。结论 Scheimpflug 成像和 U/S 厚度测量在 KC 中的 CCT 测量一致性中等。