Taping the superior aspect of patient masks qualitatively decreases air flow and bacterial dispersion towards the ocular surface while inappropriately worn masks both qualitatively and quantitatively increase bacterial dispersion towards the ocular surface.
During the COVID-19 pandemic, patients wear face masks, creating unique airflow towards the ocular surface which may complicate ocular procedures such as intravitreal injections. It has been hypothesized that oropharyngeal droplets from either the patient or physician increase the risk of post-injection infectious endophthalmitis. Prior studies have demonstrated reduced bacterial growth on culture media with simulated injections when the physician uses a face masks
In this current study, we set out to determine how patients’ wearing a mask affects bacterial dispersal in the direction of the eye as this may be a factor for intravitreal injection-related endophthalmitis.
Using schlieren imaging, we qualitatively evaluated air currents with a face mask. When focusing on the superior aspect of participant wearing a mask, schlieren imaging showed air escaping from the superior aspect of the mask. The same mask with tape covering the superior aspect showed no significant airflow towards the eye (Figure 1).
Next, to determine if the redirected air towards the ocular surface contained more bacteria, we used blood agar plates and counted the colony forming units (CFU) with different methods of mask wearing. Institutional Review Board approval was obtained through the University of Wisconsin Institutional Review Board, and all research conducted adhered to the tenets of the Declaration of Helsinki. Consenting participants were all over 18 years-old of age.
Blood agar plates with 5% sheep blood in tryptic soy agar base were incubated at 37°C in 5% carbon dioxide for 48 hours. Plates were brought to room temperature from their storage temperature of 4 degrees Celsius to eliminate variability in organism recovery rate based on initial incubation temperatures.
Participants used standard face mask with elastic ear loops and wire-containing nasal bridge (3M Company, St. Paul, MN, USA).
Control plates were held uncovered and perpendicular to the floor for 2 minutes away from the individual. In the subsequent groups, a blood agar plate was placed at each inferior orbital rim perpendicular to the floor. We enrolled 54 participants and each performed five below scenarios, instructing them to speak or count aloud for two minutes (Figure 2, available at www.aaojournal.org):
No face mask worn
Face mask fully covering the mouth but placed just below the nose (inappropriate use)
Face mask covering the mouth and nose (recommended use)
Mask covering the mouth and nose, with paper adhesive tape applied to seal the superior portion of the mask
The mean CFUs for each group: control 0.24 (95% CI 0.14-0.42), no mask 1.93 (95% CI 0.54-6.86), mask below the nose 0.67 (95% CI 0.34-1.30), mask appropriately worn 0.35 (95% CI 0.16-0.78) and the taped mask group 0.13 (95% CI 0.06-0.29) Table 1 and Figure 3. (available at www.aaojournal.org)
The taped mask group had 81% (95% CI: 48–93%; p=0.001) fewer CFUs than the group wearing a mask inappropriately below the nose. Fewer CFUs were also observed when the appropriately worn was compared to the below the nose worn group (47% reduction, incidence rate ratio=0.53; 95% CI: 0.32–0.87, p=0.011). There was some suggestion (p=0.08) that taped masks had lower mean CFU compared to when masks are normally worn (IRR = 0.37; 95% CI: 0.12–1.13). Taped masks also had 73% fewer CFUs (95% CI: 26–90% fewer, p=0.011) than the average CFUs for other non-taped forms of wearing a mask (appropriate and inappropriately worn grouped together).
We did not find taping the superior aspect of a mask to decrease bacterial dispersal towards the ocular surface when compared to an appropriately worn mask. Even more importantly, this study only looked at bacterial dispersal towards the ocular surface and did not evaluate for endophthalmitis, this would be extremely difficult owing to its low prevalence. We hypothesize that taping the superior aspect of a mask decreases dispersal of bacteria towards the eye based on the statistical trend and schlieren imaging taken together. Further studies are needed to evaluate bacterial dispersal.
During the planning stage of the study, we anticipated greater separation between these groups. Based on current best estimates, and still intending to detect at least a 2-fold separation between mean CFUs, a replication study involving only these two groups would need 72 subjects to have ∼81% chance of identifying such an effect at the 0.05 level, assuming separation of at least that size genuinely exists.
Many recommend a “no talk” policy, by both the physician and patient, during intravitreal injections to help prevent excessive bacterial dispersal towards the ocular surface.
After a small pilot study, we chose to have the subjects speak for 2 minutes as this did improve culture yields. But for our intravitreal injections performed in clinic, we have everyone in the room maintain a “no talk” policy unless essential information needs to be relayed. Additional limitations of this study include not controlling for facial shape, anatomy or hair. We also did not determine what species of bacteria grew on these plates.
Other benefits may exist for taping face masks, as condensation often forms on glasses during acuity checks and on examination lenses during slit lamp and indirect examination. Also, when the mask is taped to the patient’s face, it reduces the temptation for the patient to lower or remove the mask during the visit.
Overall, we did not show less bacteria being dispersed towards the ocular surface when comparing appropriately worn masks to masks with the superior edge taped. However, inappropriately worn masks direct more bacteria towards the ocular surface and taping the superior aspect of patient masks redirects air away from the eye, as shown with schlieren imaging, but the clinical significance could not be determined in this study. This data should serve for hypothesis generation and to help guide future directions which could examine how taping the superior aspect of a mask affects bacterial dispersal.
This work was supported in part by an unrestricted grant from Research to Prevent Blindness to the University of Wisconsin. Statistical analysis was supported through the NIH Clinical and Translational Science Award (CTSA) program (grant UL1TR002373). The funding organizations had no role in the design or conduct of this research. The schlieren imaging components were funded through the Retina Research Foundation Edwin and Dorothy Gamewell Professorship. The sponsor or funding organization had no role in the design or conduct of this research.
Conflict of Interest: No conflicting relationship exists for any author
Acknowledgements: Angela Adler and Jennie Perry-Raymond of the Clinical Eye Research Unit (CERU) at the University of Wisconsin for their support and participation.