Repeatability of wide-field choroidal thickness measurements using enhanced-depth imaging optical coherence tomography

Abstract

Background To examine the repeatability of choroidal thickness measurements across a 55° field, in a sample of healthy young adults using wide‐field enhanced‐depth imaging optical coherence tomography.

Methods High‐resolution wide‐field volumetric enhanced‐depth imaging scans were obtained from the right eye of 27 adults (mean age 27 ± 5 years) during two sessions, separated by 19 ± 15 days, using the follow‐up feature of the Spectralis instrument, while controlling for confounding factors known to influence choroidal thickness. Semi‐automatic segmentation of the choroidal boundaries was corrected by a single masked observer. This process was repeated on images from the first session of 12 randomly selected subjects, allowing the intersession (n = 27) and intraobserver (n = 12) co‐efficients of repeatability for regional measures of choroidal thickness to be calculated.

Results The observer‐related variability in choroidal thickness was highest at the fovea (intraobserver co‐efficient of repeatability [95% confidence interval], 13 [7–19] μm, p < 0.001), then reduced gradually toward the perifovea (2 [1–4] μm, p < 0.001), and plateaued in the near‐peripheral (2 [1–3] μm) and peripheral (4 [2–6] μm) regions. The intersession variability improved significantly from the fovea (intersession co‐efficient of repeatability [95% confidence interval], 27 [16–38] μm, p < 0.01) and parafovea (25 [15–36] μm, p < 0.02) toward the periphery (16 [10–23] μm).

Conclusion Wide‐field choroidal thickness measurements using enhanced‐depth imaging optical coherence tomography are highly repeatable in the macular region, and improve in precision in more peripheral regions in healthy young adults. A change of up to 38 and 28 μm is required to distinguish true clinical change from measurement variability in individual measurements of macular and extra‐macular choroidal thickness, respectively.