Repeatability of Epithelium Thickness Measured by an AS-OCT in Different Grades of Keratoconus and Compared to AS-OCT/Placido Topography

Yiran Wang; Rui Ning; Kexin Li; Huilin Xu; Yue Li; Yizhou Yang; Ingemar Gustafsson; Xingtao Zhou; Xiaomei Qu; Jinhai Huang

doi:10.1016/j.ajo.2024.04.001

Repeatability of Epithelium Thickness Measured by an AS-OCT in Different Grades of Keratoconus and Compared to AS-OCT/Placido Topography

Am J Ophthalmol. 2024 Apr 14:265:213-223. doi: 10.1016/j.ajo.2024.04.001. Online ahead of print.

Authors

Yiran Wang¹, Rui Ning¹, Kexin Li¹, Huilin Xu¹, Yue Li¹, Yizhou Yang¹, Ingemar Gustafsson², Xingtao Zhou¹, Xiaomei Qu³, Jinhai Huang⁴

Affiliations

¹ Eye Institute and Department of Ophthalmology, Eye & ENT Hospital, Fudan University; NHC Key laboratory of Myopia and Related Eye Diseases; Key Laboratory of Myopia and Related Eye Diseases, Chinese Academy of Medical Sciences (Y.W., R.N., K.L., H.X., Y.L., Y.Y., X.Z., X.Q., J.H.), Shanghai, China; Shanghai Research Center of Ophthalmology and Optometry (Y.W., R.N., K.L., H.X., Y.L., Y.Y., X.Z., X.Q., J.H.), Shanghai, China.
² Department of Clinical Sciencess, Ophthalmology, Lund University, Skåne University Hospital (I.G.), Lund, Sweden.
³ Eye Institute and Department of Ophthalmology, Eye & ENT Hospital, Fudan University; NHC Key laboratory of Myopia and Related Eye Diseases; Key Laboratory of Myopia and Related Eye Diseases, Chinese Academy of Medical Sciences (Y.W., R.N., K.L., H.X., Y.L., Y.Y., X.Z., X.Q., J.H.), Shanghai, China; Shanghai Research Center of Ophthalmology and Optometry (Y.W., R.N., K.L., H.X., Y.L., Y.Y., X.Z., X.Q., J.H.), Shanghai, China. Electronic address: quxiaomei2002@126.com.
⁴ Eye Institute and Department of Ophthalmology, Eye & ENT Hospital, Fudan University; NHC Key laboratory of Myopia and Related Eye Diseases; Key Laboratory of Myopia and Related Eye Diseases, Chinese Academy of Medical Sciences (Y.W., R.N., K.L., H.X., Y.L., Y.Y., X.Z., X.Q., J.H.), Shanghai, China; Shanghai Research Center of Ophthalmology and Optometry (Y.W., R.N., K.L., H.X., Y.L., Y.Y., X.Z., X.Q., J.H.), Shanghai, China. Electronic address: vip999vip@163.com.

PMID: 38621521
DOI: 10.1016/j.ajo.2024.04.001

Abstract

Purpose: To compare agreement of corneal epithelium thickness (ET) between AS-OCT system (RTVue, Optovue) and AS-OCT/Placido topographer (MS-39, CSO) in eyes with different stages of keratoconus (KC), and to assess the repeatability of RTVue AS-OCT.

Design: Prospective reliability analysis.

Methods: KC eyes were classified into forme fruste KC (FFKC), mild, moderate, and severe KC. Agreement was evaluated with Bland-Altman plots and 95% limits of agreement (LoA). The repeatability of RTVue was assessed via within-subject standard deviation (S_w), test-retest variability (TRT), coefficient of variation (CoV), and intraclass correlation coefficient (ICC).

Results: A total of 119 KC eyes were enrolled, with 21 being FFKC, 26 mild, 39 moderate, and 34 severe. The 95% LoA ranged between -5.9 and 4.8 µm for center epithelium thickness (CET), between -5.7 and 8.2 µm for thinnest epithelium thickness (TET). At 1-mm measuring points, the 95% LoA of superior, inferior, nasal, and temporal were -4.2 to 4.7 µm, -5.2 to 6.0 µm, -7.9 to 10.2 µm, and -11.2 to 6.0 µm. At 3-mm measuring points, the corresponding values were -2.8 to 9.3 µm, -2.0 to 13.0 µm, -4.6 to 9.6 µm, and -6.3 to 9.7 µm, indicating that the 2 instruments were not interchangeable without adjustment. Despite that the repeatability of RTVue measurements in KC patients were acceptable, repeatability decreased gradually with the peripheralization of the measurement points.

Conclusions: The 2 OCT-based devices, RTVue and MS-39, do not provide interchangeable measurements of epithelium thickness in KC patients. Repeatability decreases in cases of more severe KC, emphasizing the importance of grading before clinical examination to avoid diagnostic errors.

Keywords: Corneal epithelium thickness; Optical biometry; keratoconus; optical coherence tomography.