Air that escapes from patients’ face masks during the in-clinic administration of eye drops may contaminate the bottle, providing a potential mechanism for transmitting respiratory pathogens, including COVID-19. Ensuring a tight-fitting mask can help reduce the risk of contamination, according to findings published in the Journal of Cataract & Refractive Surgery.

The use of multiuse eyedrop bottles — including those for topical anesthetics, dilation agents, vital dyes, and other substances — is common in eye care facilities. SARS-CoV-2 is spread via droplets, aerosol, and possibly on objects and surfaces. Multiuse bottles are typically held close to a patient’s face during drop administration and then reused again on other patients. Although these bottles do not come into contact with the eye, researchers speculate that facemasks may direct the airflow from the patient’s mouth and nose upward, onto the dropper bottle.  Because they are used for multiple patients, these bottles then have the potential to spread COVID-19 or other respiratory pathogens, according to investigators. 

As per Centers for Disease Control and Prevention’s COVID-19 recommendations, both patients and clinical staff should wear surgical or cloth masks during patient encounters. However, many masks are worn loosely, leaving a significant gap that allows air to escape, meaning patients’ breath may come in contact with multiuse bottles, potentially transferring respiratory droplets, airborne viral particles, or other microbes, according to researchers.


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To test their hypothesis, investigators used a Schlieren airflow imaging system to evaluate breath expelled from gaps between masks and patients’ faces. During the study, images were taken of an examinee wearing a typical face mask and enacting common clinical scenarios. Interventions were used to minimize the mask gap. The team measured the maximum visible vertical breath plume height and bottle height during eye drop administration.

The findings reveal that breath plume height (mean=275.5 mm ± 16.3 mm) was significantly greater than mean bottle height (13.9 mm ± 4.7 mm; P <.01). Plume height was reduced by holding the mask tightly to the face (manual mask occlusion) vs not holding it (P <.01). Plume height also was lower than mean bottle height with manual mask occlusion (P <.01) but not in the absence of occlusion (P <.01). Neck extension alone did not adequately redirect escaped breath to prevent contact with a bottle.

To reduce risk, researchers recommend that eye care providers manually decrease any mask gap, remind patients to avoid talking, and encourage patients to extend their necks during eye drop administration. Providers may consider taping the mask around the nasal bridge instead of manually securing the mask.

This study had several limitations. First, although significant exhaled breath contact with multiuse eye drop bottles is supported by this study, researchers note that this does not necessarily suggest that infectious viral particles are directly exposed to these bottles, carried by bottles, or transmitted to other patients or clinicians via these bottles. Second, while contact was significantly reduced through manual mask occlusion, it does not necessarily reduce exposure of the bottle to airborne pathogens or respiratory droplets. It also is unknown whether infectious viral particles or other microbes may travel beyond the visible plume of breath. Lastly, the true extent of exhaled breath may not precisely correlate with the breath pattern observed with Schlieren imaging.

Reference

Garcia GA, Hines JA, Wang EW, et al. Contamination of multiuse eye drop bottles by exhaled air from patients wearing face masks during the COVID-19 pandemic: a Schlieren imaging analysis. J Cataract Refract Surg. Published online January 21, 2021. doi:10.1097/j.jcrs.0000000000000590