Primary endpoints
VEGF and PlGF were measured in the same vitreous sample by enzyme-linked immunosorbent assay (ELISA) using the Quantikine Human VEGF and PlGF kits (R&D System, Minneapolis, MN) performed according to the manufacturer’s instructions. The intra-assay and inter-assay coefficients of variation for VEGF were 5.4% and 7.3%, respectively; and 5.4% and 11.2% for PlGF, respectively.