Central serous chorioretinopathy (CSC) is a self-limiting disease affecting the macular region characterized by subretinal fluid (SRF) formation that may be accompanied by retinal pigment epithelium (RPE) detachment. SRF usually resolves on its own or quickly with some intervention, but a small percentage of affected eyes may develop chronic or relapsing, eventually leading to irreversible vision loss. Because the transition from acute to chronic CSC is rare, it is now considered possible that acute and chronic CSC are distinct disease entities. The difference between acute and chronic CSC should not depend on the time of onset, but should be based on multimodal imaging (MMI) features of the disease. Therefore, early detection of chronic CSC is helpful to predict the prognosis of the disease and take active management measures.

Current MMI biomarkers for chronic CSC are:

· Spontaneous fluorescence (AF) : widespread multiple lesions;

· Fundus fluorescein angiography (FFA) : extensive visibility of fluorescent streamers;

· Indocyanine green angiography (ICGA) : choroidal vasodilation with enhanced permeability;

· OCT: diffuse shallow SRF, shallow retinal pigmented epithelium detachment (PED), diffuse intraretinal cystoid changes, intraretinal hyperreflectance, outer retinal atrophy, choroidal neovascularization (CNV), subretinal scarring, and RPE atrophy.

However, considering that CSC is mainly a choroidal disease, it is necessary to analyze its choroidal pathological features in detail. The main features of choroidal disease include the presence of thick choroidal vessels and thinning of the inner choroid. Recently, a case series published in AJO describes a biomarker of chronic CSC called Inner Choroidal Fibrosis (ICF), which appears on OCT as a specific hyperreflective lesion in the inner choroid and may correlate with the severity of chronic CSC.

Case 1: