A multiplex bead immunoassay system (Milliplex Human Cytokine kit; Millipore Corp., Billerica, MA, USA) was used to analyze cytokine concentrations. The results were analyzed by using the Bio-Plex suspension array system (Bio-Plex200; BioRad, Hercules, CA, USA) according to the manufacturer's instructions, vitreous or venous blood samples were diluted 2-fold to 10-fold, and 100 μL diluted sample was added into each of the ELISA plates for the analysis. Interleukin (IL)-1β (cat # MLB00C), IL-6 (cat # HS600B), IL-8 (cat # VAL103), IL-10 (cat # S1000B), IL-18 (cat # AF177), CCL1 (cat # BAF272), CCL2 (cat # SCP00), CCL3 (cat # BA1265), CCL4 (cat # AJ1481b), CXCL4 (cat # DY795), CXCL9 (cat # DCX900), CXCL10 (cat # SIP100), VEGF (cat # DVE00), VEGF-R1 (cat # DRV100B), and VEGF-R2 (cat # DVR200) were purchased from R&D Systems (Minneapolis, MN, USA); CCL7 (cat # 11926-H07E), CCL8 (cat # 11989-H21E), CXCL5 (cat # 10889-HNAE), CXCL6 (cat # HG10612-M), TNF-α (cat # 10602-HNAE), IFN-γ (cat # 10338-H03HL), and sCD200 (cat # 10886-H08HL) were purchased from Sino Biological, Inc. (Beijing, China). In each ELISA kit, the detection limits were 9.0, 3.5, 355, and 25 pg/mL. The FLUOstar Omega-Miroplate reader (BMG Labtech, Offenburg, Germany) was used for the ELISA plate readings. The antibodies against each of cytokines conjugated to horseradish peroxidase were added to each well of the ELISA plate. After samples incubation into the wells of ELISA plates, substrate mix solution was added for color development. After the addition of 2 N sulfuric acid, the reaction was stopped, and optical density was read at 450 nm in a microplate reader. The actual concentration for each sample was calculated by using the four-parameter fit logistic (4-PL) curve equation. After the standard curve was obtained using 4-PL, the correction read was multiplied by the dilution factors to attain the actual reading for each sample.