Purpose: High altitude is the main area for human exploration, and human eye is an important organ for obtaining visual signals. The changes of ocular structural parameters in a simulated hypobaric hypoxia environment need to be clarified. Methods: Measurements were taken at five altitudes ((1) ground, (2) 3500 m, (3) 4000 m, (4) 4500 m and (5) ground). 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 4500 m, then decreased. Significant AL differences were observed across altitudes (p<0.05), except between 2–5 and 3–5. Central corneal thickness (CCT) thickened then thinned with elevation changes, significantly thicker at altitudes 2–5 compared with 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. Conclusions: As altitude increases and acute low-pressure hypoxia worsens, changes in AL, CCT and LT may affect pilots’ visual function, information acquisition, decision-making and flight safety.

This study identifies a critical “functional mismatch” in retinal neurovascular adaptation to acute hypoxia. We demonstrate that while superficial microvasculature sustains compensatory dilation up to simulated 4,500 m, neuronal function significantly declines. This dissociation suggests that vascular autoregulation reaches a functional ceiling, failing to sustain neural activity under severe stress. These findings establish the retina as a sensitive noninvasive model for determining the physiological limits of cerebral oxygen regulation.

Purpose: To quantify changes in colour vision immediately after exposure to different altitudes of low-pressure hypoxia. Methods: The study involved 35 healthy participants (ages 20–26). Colour vision was assessed using the Farnsworth-Munsell 100-Hue test at eight different altitudes (condition 1: ground, condition 2: 3500 m, condition 3: 3500 m after 40 min, condition 4: 4000 m, condition 5: 4000 m after 40 min, condition 6: 4500 m, condition 7: 4500 m after 40 min, condition 8: back to the ground). Data were analysed using Analysis of Variance (ANOVA), paired t-test, and χ² test . Results: Total Error Score (TES) increased with altitude and hypoxia duration, with higher TES in condition 8 than in condition 1. There were significant TES differences between conditions 3 and 7, as well as 4 and 7. Friedman and repeated ANOVA tests revealed significant sector differences, with Blue-Yellow Partial Error Score (PES) greater than Red-Green PES, particularly on conditions 4, 5 and 8. Significant Red-Green PES differences were found between conditions 4 and 7, and Blue-Yellow PES between conditions 3 and 5, 7, 8. Tritan (Blue-Yellow) shift was most pronounced at high altitudes. Conclusions: This experiment investigated acute low-pressure hypoxia’s effects on colour vision, supplementing chronic hypoxia research. Increased altitudes and exposure duration worsen colour vision, with effects persisting post-recovery. Tritan axis loss is most significant under hypoxia.