Another study involving iris specimens collected during a trabeculectomy surgical procedure has shown that, compared to POAG patients, irises from eyes suffering from PACG express a significantly higher amount of several genes: COL1A1 (collagen type I alpha 1 chain), VEGFB, VEGFC and VEGFR2 (vascular endothelial growth factors B and C and the VEGF receptor 2) [15]. This evidence concerns the gene VEGFB and open-angle glaucoma.