The landscape of retinal disease diagnosis has shifted dramatically with the emergence of the Pachychoroid Spectrum Disease (PSD). This group of chorioretinal disorders is defined by abnormal choroidal thickening and pathological changes affecting the choroid, retinal pigment epithelium (RPE), and the retina. While the term “pachychoroid” was first introduced in 2013 to describe eyes with thickened choroids, our understanding has evolved from simply measuring thickness to identifying complex vascular and structural signatures.
The Spectrum of Conditions
The pachychoroid spectrum is not a single disease but a continuous range of related conditions:
- Pachychoroid Pigment Epitheliopathy (PPE): The earliest manifestation, featuring RPE abnormalities without subretinal fluid.
- Central Serous Chorioretinopathy (CSC): Characterized by serous detachment of the neurosensory retina.
- Pachychoroid Neovasculopathy (PNV): Type 1 macular neovascularization developing in eyes with pachychoroid features.
- Polypoidal Choroidal Vasculopathy (PCV): A variant of neovascularization with aneurysmal (polyp-like) lesions.
- Peripapillary Pachychoroid Syndrome (PPS): Fluid pockets specifically around the optic disc.
- Pachyvitelliform Maculopathy (PVM): A rare entity featuring yellowish subfoveal deposits.
Why Does It Occur? The “Two-Hit” Mechanism
Recent research suggests that PSD development often follows a “Two-Hit Mechanism”:
- The First Hit (Anatomy): An individual is predisposed by anatomical factors like a thick sclera, short axial length (hyperopia), or asymmetric vortex venous drainage.
- The Second Hit (Triggers): Physiological triggers activate the disease. These include corticosteroid exposure, psychological stress, sleep disturbances, or metabolic disorders.
Additionally, the Choroidal Venous Overload Theory proposes that abnormalities in venous drainage cause congestion, leading to the development of “pachyvessels”—dilated outer choroidal vessels that compress the inner choriocapillaris.
The Power of Multimodal Imaging
Managing these conditions relies on a synergistic approach using various imaging technologies:
- Optical Coherence Tomography (OCT): Provides high-resolution cross-sections to measure Choroidal Thickness (CT) and visualize pachyvessels in Haller’s layer.
- OCT Angiography (OCTA): A non-invasive game-changer that allows doctors to see blood flow and detect macular neovascularization (MNV) without the need for dye injections.
- Indocyanine Green Angiography (ICGA): Remains the gold standard for identifying choroidal hyperpermeability (CH) and specific polypoidal lesions.
- Fundus Autofluorescence (FAF) & Infrared (IR): These tools help assess the metabolic health and integrity of the RPE.
Looking to the Future
The integration of Artificial Intelligence (AI) and deep learning is set to further advance PSD management by automatically detecting pachyvessels and quantifying flow deficits. Furthermore, advancements in ultra-widefield imaging are helping clinicians see how these vascular changes extend far beyond the central macula, potentially leading to more personalized and effective treatments like optimized photodynamic therapy (PDT).
Reference: Viggiano, P., Boscia, G., Sadeghi, E., Cheung, G., Borrelli, E., Alessio, G., Chhablani, J., & Boscia, F. (2025). Pachychoroid disease spectrum: how multimodal imaging and OCT angiography have improved our knowledge. Progress in Retinal and Eye Research, 107, 101372.
