<qa>  What is the pathophysiology of CSC?Central serous chorioretinopathy CSC is characterized by serous detachment of the neurosensory retina. The pathophysiology of CSC is not certain and various theories are proposed including impaired function of retinal pigment epithelium RPE, choroidal ischemia and choroidal hyperpermeability leading to RPE damage. Acute CSC with monofocal or paucifocal changes of RPE usually shows spontaneous resolution and has a favorable visual outcome. Chronic CSC is characterized by multifocal or diffuse decompensation of RPE associated with persistent detachment of neurosensory retina. This might lead to cystoid macular degeneration, foveal atrophy and damage to the foveal photoreceptor layer, consequently resulting in irreversible significant visual loss. Photodynamic therapy PDT was proposed for the treatment of chronic CSC. Modified parameters of PDT such as shortening of the time of laser emission and reduction of a total light energy have been suggested to reduce the irreversible damages induced by conventional PDT. Recently, intravitreal injection of antibody to vascular endothelial growth factorVEGF was proposed as a new treatment option based on the effect of anti-permeability. Several reports demonstrated acceptable outcomes after intravitreal bevacizumab injection, one of anti-VEGF agent. But the clinical results with ranibizumab are not reported yet. The purpose of this study is to compare the efficacy and safety of intravitreal ranibizumab injection versus low-fluence PDT in the treatment of chronic CSC. 