Objective To compare spectral-domain optic coherence tomography (SD-OCT) and swept-source OCT (SS-OCT) in the study of choroidal thickness (CT) in healthy eyes.

Methods Prospective, cross-sectional, single-centre study. 82 healthy eyes of 46 patients were included. In a single session, Topcon 3D-2000 SD-OCT and 1050 nm SS-OCT prototype devices were used to perform OCT scans using a single line protocol. Two masked investigators independently, manually determined 13 CT measurements consisting of one subfoveal (SFCT), and six measurements on either side of the fovea (nasal and temporal) taken every 500 microns apart. The mean CT (MCT) was the mean average of these 13 measurements.

Results SD-OCT was able to reproducibly measure the CT in 74.4% of eyes vs 100% with SS-OCT (p<0.05; Fisher's Exact test). In those eyes measured by both systems, mean SFCT was 279.4±96.9 μm (range, 84–506) with SD-OCT vs 285.7±88.9 μm (range 130–527) with SS-OCT (p=0.11; Student's t test paired data). Mean MCT was 243.8±78.8 μm (range 103.6–433.2) with SD-OCT vs 242.2±81.8 μm (range 97.6–459) with SS-OCT (p=0.64; Student's t test paired data). The difference in SFCT and MCT was not statistically significant between both devices. Intraclass correlation coefficient was higher than 0.9 interobserver and interdevice measurements. SFCT Bland–Altman plots showed 95% interobserver measurement agreement within ±34 for SD-OCT, ±22 for SS-OCT and ±60 μm intersystems.

Conclusions SS-OCT permitted accurate identification of the choroido-scleral border in 100% of normal eyes, suggesting that SS-OCT was the superior modality for the measurement of CT.