NOS has three isoforms: NOS-1 (this enzyme is associated with diminished bundles at the prelaminar region of the lamina cribrosa in glaucoma patients), NOS-2 (is associated with elevated IOP – the presence of this enzyme has a genetic predisposition), NOS-3 (vasodilator found in the prelaminar region of the optic nerve) [14,15]. This evidence concerns the gene NOS2 and glaucoma.