Comparative Night Vision Goggle Visual Acuity Measurements Performed In The A 10 Aircraft In An Operational Setting PDF Download

This paper presents the findings from a study to quantify the effect of mild hypoxia and breathing supplemental oxygen on an aircrew member's static visual acuity while using night vision goggles (NVG). In this within subjects experiment, static NvG visual acuity was measured for 15 subjects at six simulated altitude levels (i.e., ground level, 5,000, 10,000, 15,000, 18,000 and 20,000 feet). Three target contrasts (i.e., high, medium, and low) were used for each visual acuity measurement under both simulated starlight and quarter moon illumination levels. Two supplemental oxygen conditions (i.e., 100% and normal setting) were used at all altitudes and a "no" supplemental oxygen condition was used up to 10,000 feet. Overall, there was a significant decrease in average visual performance across all conditions from the equivalent of 20/44 Snellen acuity at ground level to the equivalent of 20/46 at 20,000 feet. Overall, the "100%" and "normal" oxygen conditions were not significantly different from one another. At the two lowest altitudes, the "no" supplemental oxygen condition did not differ significantly from the other two oxygen conditions. However, at the 10,000 ft. altitude, the "no" supplemental oxygen condition was significantly degraded from both the "100%" and "normal" conditions. Since this study was conducted under an existing generic altitude protocol, the results did not provide complete information on the impact on visual acuity while performing operations at 15,000 feet without supplemental oxygen, applicable to helicopter operations in the mountains. A follow-up study was recommended but not funded.