Aerosol formation during non-contact "air-puff"tonometry and its significance for prevention of COVID-19

Abstract

Objective To evaluate the aerosol and concentration (PM2.5, PM10 and aerosol particle number) formation in non-contact air-puff tonometry and provide suggestions for medical workers to take appropriate daily protection during the prevalence of 2019-nCoV. Methods A cross-sectional study was carried out in this study.Thirty healthy subjects were enrolled on February 22, 2020 in Eye Hospital of Wenzhou Medical University.The intraocular pressure (IOP) was measured by non-contact air-puff tonometer in the ophthalmic consulting room and the hall with or without masks.Particulate matter (PM)2.5, PM10 and aerosol particles were recorded by air quality detector.The cumulative effects of IOP measurement, PM2.5, PM10 and aerosol particle number were analyzed, and the aerosol density of subjects with and without masks was compared. Results The PM2.5, PM10 and aerosol particles produced by the non-contact air-puff tonometry and increased with the increase of spray times.The IOP curves of 60 eyes of 30 subjects were measured respectively in two environments of medical consulting room and medical institution hall.It was found that PM2.5, PM10 and particle number fluctuated and increased with the increase of IOP measurement person times, showing cumulative effect, and the accumulation speed of aerosol density in hall was faster than that in consulting room.The density of PM2.5 and PM10 produced without gauze mask were (53.417±2.306) and (85.350± 3.488) μg/m3, which were higher than those of (50.567±0.862) and (80.617±1.463) μg/m3 with gauze mask.The differences were statistically significant (P=0.028, 0.019), and significant difference was found in aerosol density between with and without gauze mask, although more aerosol was produced without gauze mask in comparison to gauze mask (P=0.123). Conclusions Aerosol can be produced by non-contact air-puff tonometer spraying, and it fluctuates with the increase of spraying times, showing a cumulative effect.The aerosol and particulate matter accumulation is higher in the hall with insufficient air circulation, and more aerosol and PM can be produced without gauze mask. Key words: Tonometer, non-contact air-puff; Aerosol; Particulate matter; Infection; Transmission; Corona virus disease-19