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Reliability and agreement of the central and mid-peripheral corneal thickness measured by a new Scheimpflug based imaging

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A-Yong Yu1,2#, Junming Ye1#, Giacomo Savini3 , Yiran Wang1 , Tianjiao Zhang1 , Min Chen1 ,  Qinmei Wang1,2, Jinhai Huang1,2 

1 Eye Hospital and School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, China

2 State Key Laboratory of Optometry,  Ophthalmology and Vision Science, Wenzhou, China

3 G.B. Bietti Foundation IRCCS, Rome, Italy

Contributions: (I) Conception and design: AY Yu, J Ye, Q Wang, J Huang; (II) Administrative support: Q Wang, J Huang; (III) Provision of study  materials or patients: AY Yu, J Ye; (IV) Collection and assembly of data: Y Wang, T Zhang, M Chen; (V) Data analysis and interpretation: AY Yu, G  Savini, J Huang; (VI) Manuscript writing: All authors; (VII) Final approval of manuscript: All authors.

# These authors contributed equally to this work. 

Correspondence to: Prof. Qinmei Wang, MD; Jinhai Huang, MD, PhD. Eye Hospital of Wenzhou Medical University, 270 West Xueyuan Road,  Wenzhou, China. Email: wqm6@mail.eye.ac.cn; vip999vip@163.com, vip9999vip@wmu.edu.cn. 


Background: To assess the intra-observer repeatability and inter-observer reproducibility of central  corneal thickness (CCT) and mid-peripheral corneal thickness (MPCT) measurements using a new  Scheimpflug imaging instrument (Scansys) and compare the agreement with the rotating Scheimpflug  corneal tomographer (Pentacam HR). 

Methods: The same well-trained operator performed the measuring using the two devices, after which  Scansys measurements were repeated by another operator. Both instruments required three consecutive  measurements per subject. Corneal thickness measurements were obtained by each instrument, including  CCT, thinnest corneal thickness (TCT), pupil corneal thickness (PCT), and MPCT. Test-retest repeatability  (TRT), within-subject coefficient of variation (CoV), and intra-class correlation coefficient (ICC) were used  to evaluate repeatability and reproducibility. A paired t-test was used to compare the differences between  Scansys and Pentacam, and the agreement was compared with Bland-Altman plots. 

Results: This study enrolled 112 healthy subjects. The CoV were <0.91% and 0.55% for repeatability and  reproducibility, respectively. The ICC was close to 1 in all measurements. For intra-observer repeatability  in the CT2mm region, TRT was <10.30 µm. Moreover, TRT was <15.26 µm within the CT5mm region. The  paired t-test showed significant differences in all corneal thickness measurements (P<0.001). The central  region and CT2mm agreement were high, but the largest range of 95% limits of agreement (LoA) appeared in  the CTnasal-5mm. 

Conclusions: The new Scheimpflug imaging instrument showed excellent intra-observer repeatability  and inter-observer reproducibility for corneal thickness measurements. The agreement analysis suggested  that Scansys and Pentacam could be interchangeably used between the central region and CT2mm, except  CT5mm.


A-yong Yu, et al. Reliability and agreement of the central and mid-peripheral corneal thickness measured by a new Scheimpflug based imaging.pdf


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