Abstract
Purpose :
Retinal shape can be derived from distortion-corrected optical coherence tomography (OCT) scans. This parameter is of potential use in myopia research and in retina-related pathologies. The purpose of the study is to evaluate the metrological aspects of retinal shape estimation from OCT images covering a 90° field of view.
Methods :
A total of 20 right eyes with refractive errors ranging from 0 to -11 diopters were imaged with a swept-source OCT system (PLEX® Elite 9000; ZEISS, Dublin, CA). Three horizontally and vertically oriented line scans were acquired. An ultra-widefield add-on lens was mounted to the system to image a 90° field of view. OCT images were adjusted to more accurately depict the anatomical structure of the retina using an image transform derived from an optical model (MATLAB 2020a; The MathWorks, Inc., Natick, MA, and OpticStudio 20.3.1; Zemax, LLC, Kirkland, WA), as seen in Fig1. The retinal radius of curvature (RRC) was calculated from the distortion-corrected scan. Median ± interquartile range (IQR) and the coefficient of repeatability for the RRC were calculated. A simulated tolerance analysis was performed to identify the imaging parameters likely responsible for within-subject variations. Correlation analysis between axial length and RRC was conducted.
Results :
Horizontal and vertical retinal curvatures calculated were 12.53±1.37mm and 12.83±1.28mm with coefficients of repeatability of 1.11mm and 0.49mm, respectively. The tolerance analysis predicted the axial length to be the most sensitive parameter in the retinal curvature calculation, which can lead to up to 28% error for 0 diopter refractive error. The working distance offset (8.2%), corneal radius (1.25%), crystalline lens refractive index (0.5%), x-offset (0.65%) and head tilt (0.33%) had less of an effect, resulting in a total root mean square error of 8.34%. Correlation analysis showed significant correlations for axial length with horizontal (R=0.74, p<0.001) and vertical RRC (R=0.61, p=0.005).
Conclusions :
Calculations of retinal shape are more repeatable in the vertical than horizontal scan direction. Axial length and an offset in working distance have the biggest impact on retinal shape estimation determined with 90° field of view OCT imaging. Horizontal and vertical RRC correlate positively with axial length.
This is a 2021 ARVO Annual Meeting abstract.