EDN1 and open-angle glaucoma: For all polymorphisms studied, no significant differences of genotype distributions were shown between open-angle glaucoma patients and healthy controls, although for the ET-1 polymorphism 198K>N (base change G/T in exon 5; change of lysine to asparagine) the Lys-Lys (GG) genotype tended to be more frequent than in open-angle glaucoma patients.