EDN1 and low tension glaucoma: In our research, when comparing the frequency of occurrence of particular genotypes of K198N polymorphism of the endothelin-1 gene, C1222T, C70G, and G231A of endothelin-1 gene receptor type A, no statistically significant differences were demonstrated between the study groups (normal-tension glaucoma and high-tension glaucoma), also taking into account the patients' gender.