Repeatability of choroidal thickness measurements with Spectralis OCT images

Objective To investigate the repeatability of choroidal thickness measurements determined from enhanced depth imaging optical coherence tomography (EDI-OCT) images of eyes after wearing single-vision spectacles (SV) and orthokeratology (ortho-k) lenses. Methods and analysis Two EDI-OCT images of 40 children (SV: 20, ortho-k: 20) taken at a single visit were analysed twice. Subjects in the ortho-k group had been wearing ortho-k for 1-4 weeks. The choroidal thickness was determined from each image using a graph theory-based software and, where appropriate, manual correction of choroidal boundaries was undertaken by an experienced examiner. Results The mean (±SD) choroidal thickness was 227.3±42.2 μm for the SV subjects and 251.1±54.4 μm for the ortho-k subjects. The interimage differences in choroidal thickness were -0.99±3.54 and -1.14±5.03 μm for the SV and ortho-k subjects, respectively, and the limits of agreement were +5.96 to -7.93 and +8.72 to -11.00 μm, respectively. Conclusion The coefficients of repeatability of choroidal thickness measurements from two EDI-OCT images taken at a single visit were 7.08 μm (SV) and 10.06 μm (ortho-k), suggesting that a change in choroidal thickness of less than 10 μm may not indicate a real change resulting from ortho-k lens wear.