Investigation of endothelin-1 levels in tear fluid in primary open-angle glaucoma

PURPOSE. To study endothelin-1 (ET-1) levels in tear fluid of patients with primary open-angle glaucoma (POAG) in relation to age, disease stage, and intraocular pressure (IOP). METHODS. ET-1 levels in tear fluid were measured using enzyme-linked immunosorbent assay (ELISA) in 10 healthy volunteers and 61 patients with POAG (stages I–IV). The analysis was performed with Synergy MX photometer using ELISA Kit for Endothelin-1. RESULTS. The normal ET-1 level in tear fluid was 8.57± 5.84 pg/ml. In POAG, ET-1 levels were 10.42±3.59 pg/ml at stage I, 28.70±6.11 pg/ml at stage II, 14.28±4.71 pg/ml at stage III, and 10.8±6.50 pg/ml at stage IV. After intensification of hypotensive treatment, IOP decreased from 18.55± 5.95 mm Hg to 13.27 mm Hg, correlating with a reduction in ET-1 levels from 22.83±4.82 to 12.31±2.49 pg/ml. CONCLUSION. ET-1 is a significant systemic vasoconstrictor factor playing a key role in the pathogenesis of glaucomatous optic neuropathy. Moderate-stage glaucoma is characterized by a marked increase in ET-1 levels, which may serve as a prognostic marker. Intensified hypotensive therapy, associated with IOP reduction, correlates with a decrease in ET-1 levels.