Multimodal imaging in pachychoroid spectrum

Diagnostic investigation on pachychoroid spectrum disease (PSD) has been growing along with the rapid advancement of imaging technology. In optical coherence tomography (OCT)-based studies, choroidal thickness profile, luminal and stromal choroidal ratio, and abnormalities in the neurosensory retina have demonstrated various patterns in different clinical entities related to PSD. The emerging role of OCT angiography ()CTA) has been expanded to involve the quantitative analysis of the OCTA parameters in different clinical entities of PSD and to evaluate the choriocapillaris signal void and vessel density as indicators of choriocapillaris ischemia. OCTA has broadened our knowledge in characterization and assessment of both active and quiescent choroidal neovascularization and its association with treatment response. Recent studies using indocyanine green angiography have focused on the evaluation of choroidal vascular hyperpermeability and its relationship with other pachychoroid related features. Ultra-widefield indocyanine green angiography enables observation and characterization of peripheral choroidal pathologies and their associations with macular abnormalities. Multicolor imaging is an emerging modality with the capability to demonstrate early abnormalities in PSD. We summarize all investigations reflecting the new insights into the application of multimodal imaging for PSD and focus on novel findings observed in different clinical entities with each imaging modality.