A new approach for quantifying epithelial and stromal thickness changes after orthokeratology contact lens wear

Ziying Ran; Joshua Moore; Fan Jiang; Hongmei Guo; Ashkan Eliasy; Bernardo T Lopes; FangJun Bao; Jun Jiang; Ahmed Abass; Ahmed Elsheikh

doi:10.1098/rsos.211108

A new approach for quantifying epithelial and stromal thickness changes after orthokeratology contact lens wear

R Soc Open Sci. 2021 Dec 22;8(12):211108. doi: 10.1098/rsos.211108. eCollection 2021 Dec.

Authors

Ziying Ran¹, Joshua Moore^{1

2}, Fan Jiang³, Hongmei Guo⁴, Ashkan Eliasy¹, Bernardo T Lopes^{1

5}, FangJun Bao³, Jun Jiang³, Ahmed Abass^{1

6}, Ahmed Elsheikh^{1

7

8}

Affiliations

¹ School of Engineering, University of Liverpool, Liverpool, UK.
² Department of Mathematical Sciences, School of Physical Sciences, University of Liverpool, Liverpool, UK.
³ Eye Hospital, Wenzhou Medical University, Wenzhou, People's Republic of China.
⁴ College of Biomedical Engineering, Taiyuan University of Technology, Taiyuan City, Shanxi Province, People's Republic of China.
⁵ Federal University of São Paulo, 1500 Vila Clementino, São Paulo 04021-001, Brazil.
⁶ Department of Production Engineering and Mechanical Design, Faculty of Engineering, Port Said University, Port Fuad, Egypt.
⁷ Beijing Advanced Innovation Centre for Biomedical Engineering, Beihang University, Beijing, People's Republic of China.
⁸ National Institute for Health Research (NIHR) Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, UK.

Abstract

The aim of the study was to develop an automatic segmentation approach to optical coherence tomography (OCT) images and to investigate the changes in epithelial and stromal thickness profile and radius of curvature after the use of orthokeratology (Ortho-K) contact lenses. A total of 45 right eyes from 52 participants were monitored before, and after one month of, uninterrupted overnight Ortho-K lens wear. The tomography of their right eyes was obtained using optical OCT and rotating Scheimpflug imaging (OCULUS Pentacam). A custom-built MATLAB code for automatic segmentation of corneal OCT images was created and used to assess changes in epithelial thickness, stromal thickness, corneal and stromal profiles and radii of curvature before, and after one month of, uninterrupted overnight wear of Ortho-K lenses. In the central area (0-2 mm diameter), the epithelium thinned by 12.8 ± 6.0 µm (23.8% on average, p < 0.01) after one month of Ortho-K lens wear. In the paracentral area (2-5 mm diameter), the epithelium thinned nasally and temporally (by 2.4 ± 5.9 µm, 4.5% on average, p = 0.031). The stroma thickness increased in the central area (by 4.8 ± 16.1 µm, p = 0.005). The radius of curvature of the central corneal anterior surface increased by 0.24 ± 0.26 mm (3.1%, p < 0.01) along the horizontal meridian and by 0.34 ± 0.18 mm (4.2%, p < 0.01) along the vertical meridian. There were no significant changes in the anterior and posterior stromal radius of curvature. This study introduced a new method to automatically detect the anterior corneal surface, the epithelial posterior surface and the posterior corneal surface in OCT scans. Overnight wear of Ortho-K lenses caused thinning of the central corneal epithelium. The anterior corneal surface became flattered while the anterior and posterior surfaces of the stroma did not undergo significant changes. The results are consistent with the changes reported in previous studies. The reduction in myopic refractive error caused by Ortho-K lens wear was mainly due to changes in corneal epithelium thickness profile.

Keywords: OCT; contact lenses; cornea; epithelium; eye; orthokeratology.