Endothelin-1 (ET-1) is a potent vasoconstrictor and is considered to have a key role in the regulation of ocular perfusion and glaucoma pathogenesis. High ET-1 and ET A -receptor levels are reported in patients with primary open-angle glaucoma (POAG). We compared the mean plasma ET-1 and ET Areceptor concentration of controls and patients with early and advanced POAG stage, and assessed the correlation with the retinal nerve fibre layer (RNFL) thickness. The study included a total of 75 participants, aged 45-83 years: 25 (controls), 22 (early glaucoma) and 28 (advanced glaucoma). The plasma concentration of ET-1 and ET A -receptor was determined by enzyme-linked immunosorbent assay. The RNFL thickness was evaluated with spectral-domain optical coherence tomography. The mean ET-1 concentration was lower in the control group (4.88 § 1.75 pg/mL) than in the early and advanced POAG group (6.33 § 2.38 and 6.34 § 1.56 pg/mL). Statistically significant difference was found between the mean ET-1 concentrations in controls and glaucoma patients (p = 0.029 -early glaucoma, p = 0.018 -advanced glaucoma), and no significant difference was observed between the two POAG groups (p = 0.998). The mean ET A -receptor concentration was highest in the control group (1209.28 § 314.48 pg/mL) and the differences between the three groups were significant. Significant relationship was found only between ET-1 and RNFL. This study demonstrated the role of ET-1 in glaucoma pathogenesis based on the observed significant high ET-1 and ET A -receptor plasma levels in POAG patients. A new therapeutical approach needs to be considered in some patients.

An increasing amount of data suggests a role of the eye vascular system and oxidative stress in glaucoma pathogenesis. Reports have suggested endothelin-1 (ET-1) and its receptor (ETR-A) as possible glaucoma biomarkers. This study explored the diagnostic and prognostic abilities of ET-1 and ETR-A plasma concentrations in primary open angle glaucoma (POAG). Seventy-five participants were divided into three groups: controls, early and advanced POAG stage, graded by a perimetric visual field test. All of them underwent a standard ophthalmological examination including optical coherence tomography. The statistical analysis showed a significant difference between the ET-1 values in the controls (4.88 ± 1.75 pg/mL) and the glaucoma patients, but lack of statistical significance in the glaucoma severity (early POAG: 6.33 ± 2.38 pg/mL and advanced POAG: 6.34 ± 1.56 pg/mL). The mean ETR-A values were significantly different between the three groups (controls 1209.28 ± 314.48 pg/mL, early POAG: 673.44 ± 283.02 pg/mL and advanced POAG: 992.28 ± 264.22 pg/mL). Two mathematical models were developed concerning the two perimetric indices (MD/PSD) and ETR-A in the early glaucoma group. ETR-A showed a very high diagnostic accuracy. Only ETR-A had significant diagnostic ability for advanced glaucoma after the comparison between the two glaucoma groups. Every 1 pg/mL increase in the ET-1 plasma concentration increased the possibility for early glaucoma changes by 2.124 times, whereas every 1 pg/mL increase in the ETR-A level decreased this possibility by 1%. Our results indicate that ET-1 and ETR-A could be two very good diagnostic parameters for early POAG changes.