Contact lens wear with the USAF Protective Integrated Hood/Mask chemical defense ensemble.

The Protective Integrated Hood/Mask (PIHM) chemical defense aircrew ensemble blows air from the mask's plenum across the visor at a rate of approximately 15 L/min in order to prevent fogging of the visor and to cool the aircrew member's face. This study was designed to determine the effect of the PIHM airflow on soft contact lens (SCL) dehydration, contact lens comfort, and corneal integrity. There were 26 subjects who participated in this study: 15 SCL wearers, 6 rigid gas-permeable (RGP) wearers, and 5 nonspectacle wearing controls. Contrast acuity with the 3 Regan charts, subjective comfort, and relative humidity (RH) and temperature readings under the PIHM mask were monitored every 0.5 h during 6-h laboratory rides. Slit-lamp examinations and SCL water content measurements with a hand-held Abbe refractometer were made before and after the rides. High RH under the mask may have accounted for the moderate SCL dehydration (8.3%), no decrease in contrast acuity for any group, and lack of corneal stress. Although all groups experienced some inferior, epithelial, punctate keratopathy, RGP wearers had the most significant. SCLs performed relatively well in the PIHM mask environment. Testing with other parameter designs is necessary before recommending RGPs with the PIHM system.