Choroidal thickness derived from full-volume segmentation: Comparison of spectral-domain OCT with enhanced depth imaging versus 1050nm swept source OCT

Abstract

Purpose: We compared subfoveal and global choroidal thickness (CT) in healthy volunteers imaged with enhanced-depth imaging (EDI) in spectral-domain (SD) optical coherence tomography (OCT) versus swept-source (SS)-OCT using long-wavelength imaging.

Methods: In a prospective cross-sectional study, healthy subjects were imaged within one hour with both spectral-domain (SD)-OCT using EDI (Spectralis OCT, Heidelberg Engineering) and swept-source (SS)-OCT with a light source of 1050nm wavelength (DRI OCT-1, Topcon). For both instruments, scanning patterns covering a 6mm by 6mm area with 97 B-scans (Spectralis) and 256 B-scans (DRI OCT-1) were used. Images were exported in raw format and evaluated in custom software. The retinal pigment epithelium (RPE)-Bruch’s membrane complex was automatically segmented using the Iowa Reference Algorithm. Masked readers manually segmented the choroidal-scleral interface in all B-scans. Subfoveal and global CT was computed as the distance between the RPE-Bruch’s membrane complex and the manually segmented choroidal-sclera interface and compared between the two devices.

Results: 23 eyes of 12 subjects with a mean ± standard deviation (SD) age of 23.8 ± 1.8 years were included. Mean CT was 340.4 μm ± 62.13 μm (range, 142.9 - 478.3) with Spectralis OCT and 324.95 μm ± 62.68 μm (range, 129.4 - 455.4) with DRI OCT-1. The intraclass correlation coefficient (ICC) was 0.966 (p<0.001). Mean subfoveal CT was 363.3 μm ± 51.76 μm (range, 251.7 - 433.7) with Spectralis OCT and 345.6 μm ± 53.5 μm (range, 231.4 - 431.6) with DRI OCT-1. ICC was 0.925 (p<0.001).

Conclusions: Excellent reproducibility was demonstrated for manual CT measurement between SD-OCT using EDI mode and SS-OCT with 1050nm wavelength, with approximately 5% thinner values in DRI-OCT 1. Our results may facilitate comparison of CT values between SD- and SS-OCT in a multicenter trial setting.

Keywords: 452 choroid • 552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • 550 imaging/image analysis: clinical