[Are pachychoroid diseases really a continuum?]

Whether pachychoroid macular diseases represent a true disease continuum remains unresolved. Shared choroidal features, including pachyvessels, choroidal hyperpermeability and venous outflow abnormalities as well as clinically reported transitions from pachychoroid pigment epitheliopathy/central serous chorioretinopathy (PPE/CSC) to pachychoroid neovasculopathy (PNV) and from PNV to pachychoroid aneurysmal type 1 choroidal neovascularization/polypoidal choroidal vasculopathy (PAT1/PCV) support a spectrum concept; however, the current level of evidence is low and largely based on clinical observations, retrospective cohorts and small case series with heterogeneous definitions, selected populations and usually without independent reading center assessment. Recent studies further strengthen the opposing standpoint: choroidal thickness alone is neither necessary nor sufficient, PNV likely includes different subtypes and PCV/PAT1 is etiologically heterogeneous. Epidemiological differences between classical CSC and classical PCV/PAT1 also argue against a simple linear single-disease model. Currently, a cautious, nonlinear spectrum model with possible but not obligatory progression pathways is therefore preferable to the assumption of one single disease evolving through fixed stages.