Tsai TY, Gozari G, Su YC, et al. - In this meta-regression analyses, researchers sought to evaluate changes in optic nerve sheath diameter (ONSD) at high altitude and in acute mountain sickness (AMS). Eight studies with 248 candidates comparing ONSD from sea level to high altitude, and five studies with 454 candidates comparing individuals with or without AMS, were involved. The study shows that ONSD variations are associated with altitude and appear to increase in individuals with AMS. The study's drawbacks are limited research estimates and high heterogeneity. Further large prospective studies are needed to verify the findings.