Quantitative High-speed Assessment of Droplet and Aerosol From an Eye After Impact With an Air-puff Amid COVID-19 Scenario

Abstract

Purpose: To quantify aerosol and droplets generated during noncontact tonometry (NCT) and assess the spread distance of the same. Methodology: This was an experimental study on healthy human volunteers (n=8 eyes). In an experimental setup, NCT was performed on eyes (n=8) of human volunteers under normal settings, with a single and 2 drops of lubricant. High-speed shadowgraphy, frontal lighting technique, and fluorescein analysis were used to detect the possible generation of any droplets and aerosols. Mathematical computation of the spread of the droplets was then performed. Results: In a natural setting, there was no droplet or aerosol production. Minimal splatter along with droplet ejection was observed when 1 drop of lubricant was used before NCT. When 2 drops of lubricant were instilled, a significant amount of fluid ejection in the form of a sheet that broke up into multiple droplets was observed. Some of these droplets traversed back to the tonometer. Droplets ranging from 100 to 500 µm in diameter were measured. Conclusions: There was no droplet generation during NCT performed in a natural setting. However, NCT should be avoided in conditions with high-tear volume (natural or artificial) as it would lead to droplet spread and tactile contamination.

Fluid dynamics of droplet generation from corneal tear film during non-contact tonometry in the context of pathogen transmission

“…Finally, both the fingers from Rayleigh–Taylor as well as the ligaments from the bag formation undergo Rayleigh–Plateau instability and disintegrate into ellipsoidal droplets measuring 0.2–3 mm. In a previous study, 14 we measured the mean airflow in a standard hospital setting as 0.5–1 m/s. The maximum spread radius 20 of the smallest droplets (0.2 mm in size) generated during tonometry is ∼0.5 m, which is larger than the distance between the patient and the tonometer (11 mm).…”

“…Since viruses like human T-cell leukemia/lymphotropic virus type III (HTLV-III) 11 and severe acute respiratory syndrome (SARS)-coronavirus (CoV)-2 12,13 can be present in human tears, it was conjectured that such an event is a possible source of infection. Shetty et al 14 showed using clinical studies that droplets are visibly ejected in the case of watery eyes but not for dry eyes. However, the clinical studies do not attempt a physical analysis of the underlying fluid dynamics involved in the tear film breakup and tear ejection.…”

Central Corneal Thickness Among Filipino Patients in an Ambulatory Eye Surgery Center Using Anterior Segment Optical Coherence Tomography

“…16 Moreover, the transmissibility of the Coronavirus disease 2019 (COVID-19) from the ocular surface remains indefinite; thus, contact and aerosol-generating procedures are best avoided to prevent transmission, particularly among eyes with high IOP 21 and high tear volume. 22 Thin CCT underestimates IOP, while thick CCT overestimates IOP. Thin CCT may then delay diagnosis of glaucoma and cause insufficient treatment and rapid progression of glaucoma; thus, CCT measurements should be addressed to properly comprehend the risk for glaucoma in each patient.…”

“… 16 Moreover, the transmissibility of the Coronavirus disease 2019 (COVID-19) from the ocular surface remains indefinite; thus, contact and aerosol-generating procedures are best avoided to prevent transmission, particularly among eyes with high IOP 21 and high tear volume. 22 …”

Ophthalmic surgery on a COVID-19 positive patient – First experience!

“…We operated on our first coronavirus or COVID-19 positive case (CPC), who had an extensive eyelid and canalicular tear and needed early surgery. While the risk of operating on a positive patient is high due to aerosols generated,[ 1 2 3 ] no team member refused to be a part of the surgery. We did have some hiccups which is expected given that it is our first such experience.…”