The pachychoroid spectrum of diseases including central serous chorioretinopathy (CSC), pachychoroid neovasculopathy (PNV), and polypoidal choroidal vasculopathy (PCV) constitute key areas of interest in the recent past [1, 2]. However, the pathophysiology of pachychoroid remains an enigma. Diffusely thickened choroid and pachyvessels are the predominant characteristics of this spectrum of disease with the exception of some cases of PCV that have a thin choroid [1, 3,4,5]. The terms thick choroid and pachyvessels have been difficult to define because of physiological variability. Nonetheless, it has been proposed that a choroid thicker than 300 μm and the presence of pachyvessels, which can be seen on enhanced depth spectral domain optical coherence tomography along with engorged vascular profiles observed on indocyanine green angiography (ICG) can be used by clinicians to make this diagnosis [1, 2, 6]. Several researchers have suggested that congestion of the vortex veins, leading to choroidal congestion can result in pachychoroid disease [6,7,8,9]. Alternative pathophysiological reasons include obstruction at the level of ampulla of the vortex veins [6]. To date, there is no clear understanding as to why neovascularization occurs predominantly at the peripapillary area in pachychoroid disease. Study of the veno-venous anastomosis between the vortex veins located in different quadrants of the choroid may help in understanding the pathophysiology of the pachychoroid spectrum of diseases.

Recently, Spaide et al. described choroidal flow as analogous to that of the cerebral venous circulation and highlighted the potential role of vortex vein as a resistor in the eye [10]. Vortex veins serve as choroidal drainage routes passing through the sclera. Horizontal and vertical watersheds divide the choroidal vasculature into four quadrants. Each quadrant is served by a different set of vortex veins. Vortex veins typically range from 3 to 8 in number, with 65% of people having 4 or 5 [11, 12]. In the past, researchers have tried to understand the relationship and impact of vortex vein occlusion using experimental animal studies [13]. Recent advances in multimodal imaging and ultrawidefield ICG angiography has allowed for better visualization and detailed assessment of vortex veins in defining their patterns, extent, and coverage from the center of the macula to the ampulla [6]. It has been shown that there is an asymmetry in choroidal venous outflow and asymmetric dilation of vortex veins in different quadrants in cases of CSC and PNV [7, 14].

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