Efficacy of slit lamp breath shields

Liu, John; Wang, Annie Y.; Ing, Edsel B.

PURPOSE: To evaluate the efficacy of slit lamp breath shields to prevent droplet spray from a simulated sneeze. DESIGN: Experimental study to test effectiveness of personal protective equipment. METHODS: The nozzle of a spray gun was adjusted to angularly disperse a mist of colored dye that approximated a patient sneezing on a dimensionally accurate cardboard slit lamp model. We tested the designs of six commercially available breath shields, and one breath shield repurposed from a plastic container lid. Each breath shield was sprayed in a standardized fashion three times and the amount of overspray compared with no shield was quantified. The surface area that was sprayed was calculated using Adobe Photoshop’s color range function. The average percentage of overspray of each breath shield was computed in comparison to the control. RESULTS: The breath shields ranged in surface area from 116-1254 cm(2) and the amount of overspray varied from 54% to virtually none. Larger breath shields offered better protection than smaller ones. Breath shields attached to the objective lens arm were a better barrier than those hung by the oculars of comparable size. A repurposed plastic lid breath shield was 513cm(2), was slightly curved toward the examiner’s face, and allowed only 2% overspray. The largest breath shield (1254 cm(2)) hung near the oculars and prevented essentially all the overspray. CONCLUSION: The performance of different designs of breath shields is variable. Even high functioning shields should be used in conjunction with personal protective equipment including masks, goggles and gloves, and handwashing. Ideally patients should also wear a cloth mask during all slit lamp exams.