Pachychoroid disease is a relatively novel concept proposed in ophthalmology in recent years, which describes a series of pathological conditions including chronic persistent choroidal thickening and choroidal vasodilatation, with choroid blood capillary layer capacity attenuation, choroidal vasodilation, focal or disseminated choroidal thickening, progressive retinal pigment epithelial dysfunction and choroid retinal neovascularization as characteristic symptoms.Nowadays, the definition of pachychoroid disease has gradually changed from the previous emphasis on the simple thickening of choroid to the morphological description of complex pathological conditions.The clinical manifestations of certain pachychoroid diseases have been clearly described including central serous chorioretinopathy (CSC), pachychoroid neovasculcularization (PNV), polypoid choroidal vasculopathy (PCV), focal choroidal excavation (FCE), peripapillary pachychoroid syndrome (PPS). These entities have certain characteristic choroidal vasculopathy, which may represent different clinical manifestations of the same type of pachychoroid diseaseor indicate that they have similarpathogenesis .In this article, the existing literature and recent findings about pachychoroid disease, as well as the classification and treatment of pachychoroid diseases spectrum were summarized and discussed.

Objective:To quantitatively assess the macular and choroidal capillary vessel density and foveal avascular zone (FAZ) variables in untreated central serous chorioretinopathy (CSC), polypoidal choroidal vasculopathy (PCV) patients and healthy people using optical coherence tomography angiography (OCTA), and to investigate their correlation with retinal thickness and choroidal thickness.Methods:A cross-sectional study was adopted.Fifty-five eyes of 55 Chinese adults, including 20 eyes with untreated unilateral CSC, 16 eyes with untreated unilateral PCV and 19 eyes of healthy controls, were enrolled from January 2018 to June 2021 in Shenzhen Aier Eye Hospital Affiliated to Jinan University.The 6 mm×6 mm scanning of Optovue OCTA was carried out in all the subjects.The superficial retinal vessel density (SRVD), deep retinal vessel density (DRVD), outer retinal vessel density (ORVD) and choroidal capillary vessel density (CCVD), FAZ area, FAZ perimeter and vessel density in a 300-μm-wide annular region around FAZ were measured by ReVue software of Optovue OCTA.Central foveal thickness (CFT) and subfoveal choroidal thickness (SFCT) were assessed by Optovue OCTA HD scan.Correlation between CFT, SFCT and OCTA variable, FAZ variables were evaluated by Pearson liner correlation analysis.This study adhered to the Declaration of Helsinki.The study protocol was approved by the Ethics Committee of Shenzhen Aier Eye Hospital Affiliated to Jinan University (No.AIERKY6236-1). Written informed consent was obtained from each subject prior to entering the cohort.Results:There were significant differences in the foveal, parafoveal and perifoveal SRVD among the three groups ( F=6.344, 9.006, 5.617; all at P<0.01). Compared with healthy control group, the foveal, parafoveal and perifoveal SRVD in CSC group as well as the foveal SRVD in PCV group were significantly increased (all at P<0.01). Compared with CSC group, the parafoveal and perifoveal SRVD were significantly decreased in PCV group (both at P<0.01). There were significantly differences in the parafoveal DRVD among the three groups ( F=3.383, P<0.05). Compared with healthy control group, the parafoveal DRVD of CSC and PCV groups was increased significantly (both at P<0.05). There were significant differences in the ORVD and CCVD among the three groups ( F=16.931, 19.412; both at P<0.001). Compared with healthy control group, the ORVD and CCVD in CSC group and the CCVD in PCV group were decreased significantly (all at P<0.001). Compared with the PVC group, the ORVD was significantly decreased in CSC group ( P<0.001). A significantly difference was found in CFT among the three groups ( F=20.495, P<0.001). Compared with healthy control and PCV group, the CFT was significantly increased in CSC group (both at P<0.001). No significant difference was found in SFCT, FAZ area, FAZ perimeter and vessel density of the 300-μm-wide annular region around FAZ among the three groups ( F=1.083, 0.906, 0.819, 1.530; all at P>0.05). Negative correlations were found between parafoveal DRVD, ORVD and CFT in CSC eyes ( r=-0.555, -0.516; both at P<0.05), and a significant negative correlation was found between ORVD and CFT in PCV eyes ( r=-0.585, P<0.05). No significant correlation was found between OCTA variables (SRVD, DRVD, ORVD, CCVD), FAZ parameters (FAZ area, FAZ perimeter and vessel density of the 300-μm-wide annular region around FAZ) and SFCT in the three groups (all at P>0.05). Conclusions:Hyperaemia in the superficial capillary of macular fovea and atrophy of choroidal capillaries may be the same pathogenesis between CSC and PCV.The vessel density of outer retinal layer is a common independent influencing factor of CFT between the two diseases.