Repeatability of epithelium thickness measured by an AS-OCT in different grades 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 keratoconus and compared to AS-OCT/Placido topography

Am J Ophthalmol. 2024 Apr 13:S0002-9394(24)00140-5. 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, Institute for Medical and Engineering Innovation, Eye & ENT Hospital, Fudan University; NHC Key Laboratory of Myopia (Fudan University), Key Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, China; Shanghai Research Center of Ophthalmology and Optometry, Shanghai, China.
² Department of Clinical Sciences, Ophthalmology, Lund University, Skåne University Hospital, Sweden.
³ Eye Institute and Department of Ophthalmology, Institute for Medical and Engineering Innovation, Eye & ENT Hospital, Fudan University; NHC Key Laboratory of Myopia (Fudan University), Key Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, China; Shanghai Research Center of Ophthalmology and Optometry, Shanghai, China. Electronic address: quxiaomei2002@126.com.
⁴ Eye Institute and Department of Ophthalmology, Institute for Medical and Engineering Innovation, Eye & ENT Hospital, Fudan University; NHC Key Laboratory of Myopia (Fudan University), Key Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, China; Shanghai Research Center of Ophthalmology and Optometry, 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, Fremont, USA) and AS-OCT/Placido topographer (MS-39, CSO, Florence, Italy) in different stages keratoconus (KC) eyes, 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: Totally, 119 KC eyes were enrolled, with 21 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 1mm 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, -11.2 to 6.0 μm. At 3mm measuring points, the corresponding values were -2.8 to 9.3 μm, -2.0 to 13.0 μm, -4.6 to 9.6 μm, -6.3 to 9.7 μm, indicating the two instruments weren't interchangeable without adjustment. Despite the repeatability of RTVue in KC patients were acceptable, repeatability decreased gradually with the peripheralization of the measurement points.

Conclusions: The two OCT-based devices, RTVue and MS-39, don't provide interchangeable measurements of ET in KC patients. Repeatability decreases in severer KC, emphasizing the importance of grading before clinical examination to avoid diagnostic errors.