Choroidal morphology under pachydrusen

Importance To reveal choroidal morphological profiles under pachydrusen. Background Drusen in pachychoroid disorders show certain differences from conventional drusen and are recently named as “pachydrusen.” This study analysed the specific choroidal morphology under pachydrusen. Design This study is a cross‐sectional case series. Participants Enrolled were 136 eyes with pachydrusen from 134 patients. Methods The presence of pachydrusen in fundus area covered by a 12 × 9 mm 2 optical coherence tomography (OCT) image was accessed in eyes with pachychoroid‐related diseases or their fellow eyes using colour fundus photography and swept source OCT. Choroidal morphology under the pachydrusen was analysed using OCT B‐scans and en face images. Main Outcome Measures Choroidal thicknesses and topographical correlation between pachydrusen and pachyvessels. Results A total of 225 pachydrusen in 136 eyes were analysed. The mean number of pachydrusen was 1.65 ± 1.07 per eye. Most pachydrusen were located para‐ or perifoveally (37 subfoveal, 86 parafoveal and 102 perifoveal). The proportion of Haller's layer to total choroidal thickness was higher at the area of the pachydrusen compared to the subfovea (0.881 ± 0.081 vs 0.765 ± 0.111, P  < 0.001). In multimodal image analysis, 90.1% of pachydrusen identified using fundus photography and OCT B‐scan were located at the area of a dilated Haller vessel (pachyvessel) seen on en face images. Conclusions and Relevance Choroidal morphology under the pachydrusen showed increased Haller's layer thickness with an attenuated choriocapillaris layer, which is the hallmark of pachychoroid definition. Topographically, their locations correlated with the underlying pachyvessel.