ET‐1 plasma levels and scleral rigidity as risk factors in neovascular age‐related macular degeneration

Purpose To study the ocular blood flow, the corneal biomechanics, the scleral rigidity and the endothelin-1 (ET-1) plasma levels in patients with neovascular age-related macular degeneration (ARMD). Methods We enrolled 20 patients with ARMD and 20 age-matched control patients. Retrobulbar blood flow was examined by Colour Doppler Aplio 500 (Toshiba Medical System, Tokyo, Japan). Peak systolic velocity (PSV) and resistivity index (RI) was measured from ophthalmic artery (OA), central retinal artery (CRA) and posterior ciliary arteries (PCA’s). The corneal hysteresis CH and the corneal resistance force (CRF) values were achieved by Ocular Response Analyzer (ORA). Scleral rigidity (E) was determined by using Friedenwald nomograms. ET-1 plasma levels were determined using a specific radioimmunoassay (Sigma-Aldrich, Merck, Germany). Results We found a statistically significant difference in the CRF between patients with ARMD and control subjects (ARMD 11.23 ± 1.30 vs. Controls 9.82 ± 1.37; p<0.0025) was found. The CH index between patients with ARMD and control subjects was not statistically significant (ARMD 10.15 ± 1.25 vs. Controls 10.02 ± 1.70; p<0.617). With CDI in PCA’s we found PSV (ARMD 12.37 ± 2.80 cm/sec vs. Controls 15.44 ± 3.59 cm/sec; p<0.0063); RI (ARMD 0.80 ± 0.03 vs Controls 0.74 ± 0.02; p<0.0001). The E had a significant increase in ARMD group (ARMD 0.0358 ± 0.004 vs. Controls 0.0328 ± 0.004; p<0.008) as well as ET-1 plasma levels (ARMD 2.060 ± 0.276 vs. Controls 1.492 ± 0.0.560; p<0.001). Finally, in ARMD we found that the decrease of PSV and the increase of RI in PCA’s was correlated with the ET-1 plasma levels (PSV r-0.615; p<0.0039 and r 0.764; p<0.0001) and not with the values of E, CH and CRF. Conclusions Our data indicate that patients with neovascular ARMD had a significant increase of RI in all vessels examined with increased corneal CRF index, scleral rigidity values and ET-1 plasma levels. The decreased blood flow in APC’s was correlated to the increase of ET-1 plasma levels. These data indicate that elevated plasma ET-1 and not the scleral rigidity may be an important risk factor in the development of neovascular ARMD.