The Effect of Glare on Regan Contrast Letter Acuity Scores Using Dye-Based and Reflective Laser Eye Protection
Final rept. Aig 1998-Apr 2001
VERIDIAN BROOKS AFB TX
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Current laser eye protection devices LEPDs are dye-based or reflective. While both technologies block the laser wavelengths, reflective LEPDs generally transmit more visible light than do dye-based LEPDs. Consequently reflective LEPDs are generally superior to dye-based LEPDs for the sparse light conditions of night. Reflective LEPDs are also better at maintaining a constant color appearance which is important for tasks requiring recognition of color coded information such as reading color maps or color cockpit displays. The advantages of reflective LEPDS, higher light transmission and better color recognition, need to be considered in association with other optical qualities of reflective LEPDs. One significant measure of optical quality is haze, which tends to be higher in reflective LEPDs. Wearing an LEPD with high haze can accentuate the impact of glare. Glare reduces visual acuity, particularly at low contrast levels. Differences in contrast acuity between dye-based and reflective LEPDs were investigated in the current experiment. Under indoor lighting photopic contrast acuity was separately measured with and without glare. In the absence of glare, contrast acuity remained high with all LEPDs. Only small decrements in the ability to identify very low contrast stimuli were found. In the presence of glare, the ability to identify low contrast stimuli was substantially reduced while wearing the reflective LEPDs with higher haze. While reflective LEPDs have been optimized for nighttime use, these data suggest that glare problems from the sun might be experienced while wearing reflective LEPD if protection is required during the day.