Three-dimensional choroidal surface topography analysis in healthy eyes based on wide-field SS-OCT volume scans

Abstract

Purpose : To study the choroidal contour map in healthy eyes and make a qualitative and quantitative assessment of the inner and outer choroidal surface in a 3-dimensional (3D) view.

Methods :
This was a retrospective study based on wide-field swept-source optical coherence tomography (wide-field SS-OCT) volumes taken from 13 healthy subjects. Images were captured using a wide-field SS-OCT device (Carl Zeiss Plex Elite 9000) with a resolution of 12mm×12mm×3mm. Choroidal inner and outer surface in 3D were obtained using our previously validated residual U-Net (ResUnet) deep learning model for choroid segmentation. Qualitative analysis of inner and outer surfaces was performed using a custom built MATLAB based 3D visualization tool. Quantitative analysis was based on maximum principal curvature (Pmax) of the surface. A 4-quadrant grid with a 1mm circle centered around fovea.

Results :
Mean age of 13 healthy subjects was 30.7 ± 5.2 years. Qualitative evaluation of 13 healthy eyes demonstrated the inner surface of choroid (choroid-retinal interface) to be bell shaped in 4 eyes, hump shaped in 3 eyes, crescent shaped in 2 eyes, arc shaped in 2 eyes and cupid’s bow shaped in 2 eyes. Outer surface (chorio-scleral interface) was bell shaped in 2 eyes, hump shaped in 6 eyes, crescent shaped in 2 eyes, arc shaped in 1 eye and cupid’s bow shaped in 2 eyes. On quantitative evaluation, the mean central P_max at the inner and outer choroidal boundary was -0.23 ±1.27 and 1.09 ±3.63 respectively and were significantly different from each other (p=0.0002). Mean P_max in the superior, inferior and temporal macula were also significantly different between inner and outer choroidal surface (p=0.00003, 0.0004 and 0.003 respectively), while nasal curvatures were almost similar on both surfaces (p=0.011).

Conclusions :
A 3-dimensional view of inner and outer choroidal surface for the choroidal contour mapping is a unique way of evaluating choroid. The inner and outer choroidal contour curvature values are significantly different at the central macula, superiorly, inferiorly and at the temporal macula. Normative database for different age groups is being established and more data will be presented at the conference.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.

 

Graphical user interface showing qualitative and quantitative analysis for a healthy eye using 3D reconstruction.

 

Qualitative analysis in 3D demonstrated hump-shaped CIS and COS of a healthy eye.