Dynamics of Aerosol Generation during Eye Procedure in Context of COVID-19

Non-invasive medical diagnostics demonstrate a propensity for droplet generation and should be studied to devise risk mitigation strategies against the spread of the SARS-CoV-2 virus. We investigate the air-puff tonometry, which uses a short-timed air-puff to applanate the human eye in a bid to detect the early onset of glaucoma by measuring the intraocular pressure. The air-puff consists of a vortex trailed by a high-speed jet. High-speed imaging of the eye during a typical tonometry measurement reveals a sequence of events starting with the interaction between the tear layer and the air puff leading to an initial sheet ejection. It is immediately followed by the trailing jet applanating the central corneal section, causing capillary waves to form and interact with the highly 3D transient expanding sheet. Such interaction with the capillary waves and the surrounding airfield due to the trailing jet causes the expanding sheet to undergo bag breakup, finger formation by Rayleigh Taylor instability and further break up into subsequent droplets by Rayleigh Plateau instability, which eventually splashes onto nearby objects, potentially forming fomites or aerosols which can lead to infections. The complex spatiotemporal phenomenon is carefully documented by rigorous experiments and corroborated using comprehensive theoretical analyses.