  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.
