Night vision goggles, laser eye protection, and cockpit displays

The increasing use of lasers on the modem battlefield may necessitate the wear of laser eye protection devices (LEPDs) by warfighters. Unfortunately, LEPDs that protect against visible laser wavelengths often reduce overall light transmittance and a wearer's vision can be degraded, especially in low light conditions. Wearing night vision goggles (NVGs) provides laser eye protection behind the goggles, but NVGs do not block lasers that might enter the eye around the NVGs. Therefore, LEPDs will be worn under NVGs. People wearing NVGs look below the NVGs to read displays and for other near vision tasks. This effort involved determining the effects of wearing variable density filters on vision in low light conditions, with and without the presence of a simulated head-down display (HDD). Each subject's visual acuity was measured under moonlight illumination levels while wearing neutral density filters and LEPDs. Similar measurements of the subjects' visual detection thresholds, both on and off-axis, were made. Finally, the effects of wearing variable density filters on visual acuity on the HDD were determined. Wearing variable density filters in low-light conditions reduces visual acuity and detection. The presence of the HDD reduced acuity slightly through variable density filters but. the HDD had no effect on on-axis detection and actually improved off-axis detection. The reasons for this final finding are unclear.