Comparison of breath-guards and face-masks on droplet spread in eye clinics

COVID-19 has impacted ophthalmic care delivery, with many units closed and several ophthalmologists catching COVID-19. Understanding droplet spread in clinical and training settings is paramount in maintaining productivity, while keeping patients and practitioners safe.

We aimed to assess the effectiveness of a breath-guard and a face mask in reducing droplet spread within an eye clinic.

We performed a randomised trial of droplet spread using a fluorescein-based cough model to assess the efficacy of a 'breath-guard' and 'face-mask' to prevent the spread of droplets. The 'cough' spray was collected on calibrated paper targets. The sheets were photographed under blue light, with an orange filter on the camera; the position and size of the spots was measured with software originally developed for astronomy. We performed 44 randomised coughs; 22 controls with no breath-guard or face-mask, 11 using breath-guard only and 11 with combined breath-guard and face-mask. We compared both the number of droplets detected and the area of drops on paper targets.

The average number of droplets in the controls was 19,430 (SE 2691), the breath-guard group 80 (SE 19) droplets (P < 0.001); in the combined In the group the count was 5 (SE 2), a significant drop from shield only (P = 0.008). The mean areas of each target covered by spots for each group were 5.7 ± 0.857% (95% CI), 0.004 ± 0.000104% (95% CI) and 0.001 ± 0.0000627% (95% CI) respectively.

These results show that the breath-guard alone reduced the droplet count by 99.93%. Combining the breath-guard with a face-mask reduced the droplet count by over 99.98%. Breath-guards are widely used in clinics and this trial demonstrates that breath-guards with face-masks effectively block droplet spray.