Efficacy of Slit Lamp Breath Shields

To evaluate the efficacy of slit lamp breath shields to prevent droplet spray from a simulated sneeze.

Experimental study to test the effectiveness of personal protective equipment.

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. The designs of 6 commercially available breath shields and 1 breath shield repurposed from a plastic container lid were tested. Each breath shield was sprayed in a standardized fashion 3 times, and the amount of overspray was compared to spray with no shield and quantified. The surface area that was sprayed was calculated using a commercially available software with color range function. The average percentage of overspray of each breath shield was computed in comparison to the control.

The breath shields ranged in surface area from 116 to 924 cm², 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 better barriers than those of comparable size hung by the oculars. A repurposed plastic lid breath shield, 513 cm², was slightly curved toward the examiner's face and allowed only 2% overspray. The largest breath shield (924 cm²) hung near the oculars and prevented essentially all overspray.

The performance of different designs of breath shields was 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 face mask during all slit lamp examinations.