New insights into changes in ocular structural parameters in a simulated hypobaric hypoxia plateau environment

Abstract Purpose High altitude is the main area for human exploration, and human eye is an important organ for obtaining visual signals. The changes of eye structure and function caused by hypobaric hypoxia environment need to be clarified. Methods Measurements were taken at five altitudes (1: ground; 2: 3500m; 3: 4000m; 4: 4500m; and 5: end of experiment). Refractive values were measured with the IOL Master (Carl Zeiss Shanghai Co. Ltd.). Data analysis was performed using the Kolmogorov–Smirnov (K-S) test, paired sample T-test, and Wilcoxon test. Results Subjects’ axial length (AL) increased with altitude, peaking at 4500m, then decreased. Significant differences in AL were observed across altitudes (p < 0.05), except between 2 and 5, and 3 and 5. Central corneal thickness (CCT) thickened then thinned with elevation changes, significantly thicker at altitudes 2–5 compared to the baseline (p < 0.05). Lens thickness (LT) followed a similar pattern, increasing up to altitude 4, then decreasing at 5. Correlations were found between AL and LT at altitudes 1 (r = 0.375, p < 0.05) and 5 (r = 0.341, p < 0.05), and between AL and CCT at altitude 4 (r = 0.337, p < 0.05), but not elsewhere. No significant relationship was observed between LT and CCT. Conclusions As altitude increases and the degree of acute low-pressure hypoxia worsens, the refractive parameters such as AL, CCT, and LT are altered, which could potentially affect the pilot's visual function after acute hypoxia, further affecting the pilot's information acquisition and decision-making during driving and posing a threat to flight safety.