Impact of axial length correction on retinal and choroidal thickness by widefield optical coherence tomography

The effect of axial length (AL) correction on retinal and choroidal thickness measurements obtained with widefield swept-source optical coherence tomography (SS-OCT) was assessed, and we investigated whether this correction effect differed by measurement region (peripheral region vs. macula) and anatomical layer (retina vs. choroid). This retrospective observational cross-sectional study included 302 eyes from 151 participants without ocular disease. Correction-related changes in retinal and choroidal thickness and the interaction effects among AL, measurement region, and anatomical layer on these changes were assessed. Correction-related thickness changes increased significantly with longer AL. Significant interaction effects were observed between AL and measurement region and between AL and anatomical layer. Specifically, the correction effect was significantly greater in the peripheral region than in the macula, and AL-related correction effects were more pronounced in the retina than in the choroid. Results showed that AL correction had a significant and spatially heterogeneous effect on retinal and choroidal thickness measurements derived from widefield SS-OCT. The impact varied by measurement region and anatomical layer, with the largest correction-related effect observed in the peripheral retina. These findings support incorporating AL correction in widefield OCT analyses to reduce AL-dependent measurement bias and improve measurement comparability, particularly when evaluating peripheral regions.