Impact of image averaging on wide‐field choroidal thickness measurements using enhanced‐depth imaging optical coherence tomography

Abstract

BackgroundThe aim of this study was to examine the influence of B‐scan averaging on choroidal thickness using wide‐field enhanced‐depth imaging optical coherence tomography.MethodsSix high‐resolution trans‐foveal horizontal enhanced‐depth imaging line scans (spanning a 60° field) were acquired consecutively from the right eye of 10 healthy adults (mean age 30 ± 5 years), with each line scan an average of 10, 20, 30, 40, 50 or 100 B‐scans, using the automated real‐time image averaging and follow‐up features of a Spectralis device. The impact of B‐scan averaging on regional measures of wide‐field choroidal thickness (across macular and peripheral regions) and their accuracy was investigated, assuming that averaging 100 B‐scans would provide the most accurate estimate of choroidal thickness.ResultsRegional estimates of wide‐field choroidal thickness did not vary across the different B‐scan averaging conditions (all p > 0.05). The mean choroidal thickness averaged across the full wide‐field area exhibited the closest agreement to measures obtained with 100 averaged B‐scans, when frame averaging exceeded 30 B‐scans (95 per cent limits of agreement +10 to −7, +7 to −7 and +6 to −3 μm for 30, 40 and 50 averaged B‐scans, respectively), compared to 10 and 20 averaged B‐scans (95 per cent limits of agreement +13 to −8 and +13 to −6 μm, respectively; p < 0.01 and p < 0.02 compared to the accuracy of 50 averaged B‐scans).ConclusionAveraging 30 B‐scans for an individual enhanced‐depth imaging optical coherence tomography line scan provided accurate measures of choroidal thickness across a wide‐field (60°) area in young healthy eyes. This information can assist in designing the volumetric scan protocols required for detailed examination of the macular and peripheral choroid.