Agreement and Repeatability of Corneal Thickness and Radius among Three Different Corneal Measurement Devices

Abstract

SIGNIFICANCE:Corneal refractive surgery screening, orthokeratology, and contact lens fitting require accurate estimation of the corneal thickness and curvature. We found that any of the imaging devices used in this study can be used to image a healthy myopic cornea, which is essential to screen for corneal ectasia. PURPOSE: This study aimed to compare agreement and repeatability of corneal thickness and radius measurements obtained using Scheimpflug imaging (Pentacam HR), swept-source optical coherence tomography (Casia SS-1000), and Placido-Scheimpflug tomography (Topographic Modeling System, version 5 [TMS-5]). METHODS: Sixty eyes of 60 subjects with myopia were measured with Casia, TMS-5, and Pentacam for their central corneal thickness (CCT), thinnest corneal thickness, central corneal radius of the steep meridian (Ks), central corneal radius of the flat meridian (Kf), mean central corneal radius (Km), and anterior and posterior best-fit spheres. Two readings were obtained from each instrument. Central corneal thickness was also measured with ultrasound pachymetry. Intraclass correlation coefficient, repeatability coefficient, and coefficient of variation were calculated.RESULTS: Repeatability coefficient, coefficient of variation, and intraclass correlation coefficient of CCT among the instruments ranged between 2.48 and 12.79, 0.17 and 0.86, and 0.98 and 1.00, respectively. Mean CCT measurements were similar between Casia, TMS-5, Pentacam, and ultrasound pachymetry ( P = .13). Intraclass range of correlation for agreement was 0.95 to 0.99 for CCT among instruments. The range of 95% limits of agreement (LoAs) for ultrasound CCT was narrowest with Casia (31.94 μm). Casia-TMS-5 displayed a narrow range of 95% LoA for CCT (12.14 to −12.44), thinnest corneal thickness (12.31 to −11.31), and Ks (0.56 to −0.53), whereas Casia-Pentacam showed a narrow range of 95% LoA for Kf (0.56 to −0.42), Km (0.41 to −0.27), and anterior best-fit sphere (0.03 to −0.07). A significant difference in posterior best-fit sphere measurements was noted among all instruments ( P = .01).CONCLUSIONS: Casia, TMS-5, and Pentacam can be used interchangeably to measure corneal thickness and radius measurement in healthy eyes. Casia had the best agreement with ultrasound pachymeter CCT and exhibited the highest repeatability.

Repeatability assessment of anterior segment biometric measurements in myopic patients using a new anterior segment OCT with Placido corneal topography and agreement with a swept-source OCT

“…Previous studies [16,[18][19] on healthy eyes obtained average values of TCT between 530 and 550 µm with AS-OCT, which are comparable to the reported average of 531.85 ± 34.08 µm in this study. The repeatability of TCT measurements with MS-39 was improved compared with the reported CASIA SS-1000 measurements in the literature [18,19]. Savini et al [16] evaluated the repeatability of TCT measurements with MS-39, acquiring a CoR of 4.77 µm, a CoV of 0.32%, and an ICC of 0.999.…”

“…In terms of CCT measurement, excellent repeatability was con rmed by the small COR (1.94µm) and CoV (0.131%) scores and the ICC of 0.9996 from the current study. Measurements of CCT from MS-39 produced mean values (535.99 ± 34.17 µm) comparable to those previously reported using SS-OCT on healthy eyes [18][19][20][21][22][23]. Previous studies on myopic eyes showed that Pentacam HR rotating Scheimp ug camera and Sirius Scheimp ug camera-Placido topographer (CSO, Scandicci, FI, Italy) achieved inferior repeatability [24][25][26].…”

“…A previous study by Chan et al [18] showed that the repeatability of K s , K f and K m acquired from CASIA SS-1000 and Pentacam HR rotating Scheimp ug camera (Oculus Inc., Lynnwood, WA, US) was comparable to the current study. Biswas et al [19] compared the repeatability of keratometric measurements with CASIA SS-1000, Pentacam HR and Topographic Modeling System, version 5 (TMS-5, Tomey Corp., Nagoya, Japan), and showed that the CASIA SS-1000 and Pentacam HR presented similar repeatability with this study, while TMS-5 showed relatively inferior results. Only the repeatability of K m was evaluated in the study from Panthier et al [20], who reported that IOL Master 700 (Carl Zeiss, Germany) and Anterion (Heidelberg Engineering GmbH, Heidelberg, Germany), which both belong to SS-OCT, showed good repeatability when measuring K m , the result of which was comparable to the current study.…”

“…There are advantages as well as limitations in this study, compared with previous studies. The most important advantage is the large population examined, which included 235 eyes from 235 myopic patients, considerably more than previous studies [16,[18][19][20][21][22][23]. Additionally, only the right eye from each participant was measured, which eliminated the bias generated from bilateral-eye data.…”

Comparison of corneal tomography using a novel swept-source optical coherence tomographer and rotating Scheimpflug system in normal and keratoconus eyes: repeatability and agreement analysis

“…Moreover, there is currently no consensus, if different technologies, such as OCT, Scheimpflug or ultrasound, when assessing corneal thickness, are interchangeable or if conversion factors are applicable. Several reports demonstrated a higher measured corneal thickness by RSC compared to OCT devices [ 24 , 38 , 39 ], whereas interchangeability is reported as well [ 40 ]. These discrepancies might be due to the different investigated populations and dependent on age and the presence of ocular pathologies [ 41 ].…”