Relationship between Pachychoroid and Polypoidal Choroidal Vasculopathy

Abstract

Previous clinical studies have suggested that pachychoroid can induce macular neovascularization (MNV) to develop pachychoroid neovasculopathy (PNV) and that PNV can progress to polypoidal choroidal vasculopathy (PCV). Recent studies based on the pachychoroid concept are now gradually revealing the true nature of, at least some part of, PCV. However, previous studies on PNV and/or PCV have used different frameworks for the classification of PNV, PCV, and neovascular age-related macular degeneration (nAMD). These have hampered the rapid overhaul of the understanding of PCV. Some investigators have assumed that all PCV is pachychoroid-driven whereas other investigators have classified PCV into "pachychoroid PCV" and "non-pachychoroid PCV". Furthermore, since there is no consensus as to whether PNV includes PCV, some studies have included PCV with PNV, while other studies have excluded PCV from PNV. To address these gaps, we summarize previous studies on PCV and pachychoroid. Even before the proposal of the pachychoroid concept, previous studies had suggested that PCV could be divided into two subtypes, of which one was characterized by pachychoroid features. Previous studies had also provided keys to understand relationship between PCV and PNV. We here recommend a refined conceptual framework for future studies on PNV, PCV, and nAMD. Considering the current inconsistent understanding of PCV, we should be cautious about using the term PCV until we understand the true nature of PCV.

Keywords: age-related macular degeneration; drusen-driven disease; pachychoroid neovasculopathy; pachychoroid-driven disease; polypoidal choroidal vasculopathy.

Figure 1

The framework for the subtypes of neovascular age-related macular degeneration (nAMD) in the era of the pachychoroid concept. Exudative maculopathy, previously diagnosed as nAMD, is divided into drusen-driven disease and pachychoroid-driven disease after the development of the pachychoroid concept.

Figure 2

Recommended framework for future studies on pachychoroid diseases. Among exudative maculopathy previously diagnosed as neovascular age-related macular degeneration (nAMD), typical nAMD is divided into nAMD without polypoidal lesions and pachychoroid neovasculopathy (PNV) without polypoidal lesions, and polypoidal choroidal vasculopathy (PCV) is divided into nAMD with polypoidal lesions and PNV with polypoidal lesions, after the development of the pachychoroid concept. In the era of the pachychoroid concept, nAMD includes non-pachychoroid-driven (drusen-driven) nAMD with and without polypoidal lesions, and PNV includes PNV with and without polypoidal lesions.

Figure 3

An example of the framework used in previous studies. Among exudative maculopathy previously diagnosed as nAMD, typical nAMD is divided into nAMD that is non-pachychoroid-driven (drusen-driven) and pachychoroid neovasculopathy (PNV) that is pachychoroid-driven, while polypoidal choroidal vasculopathy (PCV) is divided into macular neovascularization (MNV) with polypoidal lesions that is non-pachychoroid-driven (drusen-driven) and PCV that is pachychoroid-driven, in the era of the pachychoroid concept. nAMD includes only non-pachychoroid-driven MNV without polypoidal lesions, PNV includes only pachychoroid-driven MNV without polypoidal lesions, and PCV includes only pachychoroid-driven MNV with polypoidal lesions. An appropriate term for non-pachychoroid-driven MNV with polypoidal lesions has not yet been proposed. Since the “polypoidal CNV” had been proposed for CNV in PCV or PCV itself and the usage of “POLYPOIDAL CNV” by Yuzawa et al. differs from the originally used term “polypoidal CNV”, “POLYPOIDAL CNV” by Yuzawa et al. is written in uppercase for differentiation.

Figure 4

An example of a framework used in previous studies. Among exudative maculopathy previously diagnosed as nAMD, typical nAMD is divided into typical nAMD that is non-pachychoroid-driven (drusen-driven) and typical pachychoroid neovasculopathy (PNV) that is pachychoroid-driven, and polypoidal choroidal vasculopathy (PCV) is divided into non-pachychoroid-driven (drusen-driven) macular neovascularization (MNV) with polypoidal lesions and pachychoroid-driven MNV with polypoidal lesions, in the era of the pachychoroid concept. nAMD includes both non-pachychoroid-driven MNV without and with polypoidal lesions. PNV includes both pachychoroid-driven MNV without and with polypoidal lesions. PCV includes both non-pachychoroid-driven MNV with polypoidal lesions and pachychoroid-driven MNV with polypoidal lesions. Pachychoroid-driven MNV with polypoidal lesions should be called typical PCV and an appropriate term for non-pachychoroid-driven MNV with polypoidal lesions has not yet been proposed. Since the “polypoidal CNV” had been proposed for CNV in PCV or PCV itself and the usage of “POLYPOIDAL CNV” by Yuzawa et al. differs from the originally used term “polypoidal CNV”, “POLYPOIDAL CNV” by Yuzawa et al. is written in uppercase for differentiation.

Figure 5

Possible future framework for neovascular age-related macular degeneration (nAMD). Typical nAMD might be divided into drusen-driven nAMD without polypoidal lesions, pachychoroid neovasculopathy (PNV) without polypoidal lesions, factor X-driven AMD without polypoidal lesions, and multifactor-driven mAMD without polypoidal lesions.