Visual performance with the Aviator Night Vision Imaging System (ANVIS) at a simulated altitude of 4300 meters

This study determined if visual performance with Aviator Night Vision Imaging System (ANVIS) was degraded by the degree of hypoxia experienced at the maximum flight altitude currently authorized (U.S. Army regulations) without supplemental oxygen. Visual acuity and contrast sensitivity with ANVIS were tested under simulated starlight and full moonlight illumination in a hypobaric chamber: at ground level (93 m), 5 min and 30 min after ascent to 4300 m, and 10 min after return to ground level. Visual acuity was significantly (p < 0.05) degraded by a small amount (0.05 log minimal angle resolvable) after 30 min at 4300 m. Contrast sensitivity was not significantly degraded at any time. No significant difference between males (n = 11) and females (n = 6) on any measure of visual performance was detected. Females did have a significantly lower percent oxygen saturation of hemoglobin compared with males at altitude (72% versus 80% after 30 min). The results suggests that visual acuity ANVIS is degraded slightly after 30 min of exposure to 4300 m, although less than what would be expected with unaided night vision under these conditions.