Khaja Wassia A, Grover Sandeep, Kelmenson Amy T, Ferguson Lee R, Sambhav Kumar, Chalam Kakarla V
Department of Ophthalmology, University of Florida, College of Medicine, Jacksonville, FL, USA.
Clin Ophthalmol. 2015 Jun 12;9:1065-70. doi: 10.2147/OPTH.S81376. eCollection 2015.
Central corneal thickness (CCT) can be measured by using contact and non-contact methods. Ultrasound pachymetry (US pachymetry) is a contact method for measuring CCT and is perhaps the most commonly used method. However, non-contact methods like scanning slit topography (Orbscan II), slit-lamp optical coherence tomography (SL-OCT), and specular microscopy are also used. Not many studies have correlated the measurement of CCT with all four modalities. The purpose of this study was to compare and correlate the CCT measurements obtained by US pachymetry with SL-OCT, specular microscopy, and Orbscan.
This is a prospective, comparative study done in an institutional setting. Thirty-two eyes of 32 subjects with no known ocular disease and best-corrected visual acuity of 20/20 were enrolled. CCT measurements were obtained using SL-OCT, specular microscopy, scanning slit topography (Orbscan), and US pachymetry. Three measurements were made with each instrument by the same operator. Mean, standard deviation, and coefficient of variation were calculated for CCT measurements acquired by the four measurement devices. Bland-Altman plot was constructed to determine the agreements between the CCT measurements obtained by different equipment.
The mean CCT was 548.16±48.68 μm by US pachymetry. In comparison, CCT averaged 546.36±44.17 μm by SL-OCT, 557.61±49.92 μm by specular microscopy, and 551.03±48.96 μm by Orbscan for all subjects. Measurements by the various modalities were strongly correlated. Correlations (r (2)) of CCT, as measured by US pachymetry compared with other modalities, were: SL-OCT (r (2)=0.98, P<0.0001), specular microscopy (r (2)=0.98, P<0.0001), and Orbscan (r (2)=0.96, P<0.0001). All modalities had a linear correlation with US pachymetry measurements.
In subjects with healthy corneas, SL-OCT, specular microscopy, and Orbscan (with correction factor) can be used interchangeably with US pachymetry in certain clinical settings. The four modalities showed significant linear correlations with one another.
中央角膜厚度（CCT）可通过接触式和非接触式方法进行测量。超声测厚法（US测厚法）是一种测量CCT的接触式方法，可能也是最常用的方法。然而，非接触式方法如扫描裂隙地形图（Orbscan II）、裂隙灯光学相干断层扫描（SL-OCT）和镜面显微镜检查也被使用。没有多少研究将CCT的测量与这四种方法进行关联。本研究的目的是比较并关联通过US测厚法与SL-OCT、镜面显微镜检查和Orbscan获得的CCT测量值。
这是一项在机构环境中进行的前瞻性比较研究。纳入32名无已知眼部疾病且最佳矫正视力为20/20的受试者的32只眼。使用SL-OCT、镜面显微镜检查、扫描裂隙地形图（Orbscan）和US测厚法获得CCT测量值。由同一名操作者使用每种仪器进行三次测量。计算通过四种测量设备获得的CCT测量值的平均值、标准差和变异系数。构建Bland-Altman图以确定不同设备获得的CCT测量值之间的一致性。
US测厚法测得的平均CCT为548.16±48.68μm。相比之下，所有受试者通过SL-OCT测得的CCT平均为546.36±44.17μm，通过镜面显微镜检查测得的为557.61±49.92μm，通过Orbscan测得的为551.03±48.96μm。各种方法的测量结果高度相关。与其他方法相比，US测厚法测得的CCT的相关性（r²）分别为：SL-OCT（r²=0.98，P<0.0001）、镜面显微镜检查（r²=0.98，P<0.0001）和Orbscan（r²=0.96，P<0.0001）。所有方法与US测厚法测量值均呈线性相关。
在角膜健康的受试者中，在某些临床环境下，SL-OCT、镜面显微镜检查和Orbscan（校正因子）可与US测厚法互换使用。这四种方法相互之间显示出显著的线性相关性。
