■ Researchers described how the flow of energetic gas can transform a thin liquid film into droplets, to show how noninvasive ocular diagnostics can distribute pathogens like the novel coronavirus. PhD student Durbar Roy and colleagues described their mechanistic understanding of the droplet creation and transmission scenario that may occur during ophthalmic tests in Physics of Fluid. They used linear stability theory to predict the “journey of the tear from sheet to droplets” and corroborated their theory via high-speed imagery. Air puff tonometry’s interaction with the tear film creates submillimeter-sized droplet projectiles traveling at speeds of 0.2 m/s, they found. The spread radius the investigators calculated shows the likelihood of tonometry’s ability to create and disperse droplets into the air — which could splash on instruments — and subsequently increase infection risk.

“In the context of medical tests such as the tonometry, it is apparent that routine procedures can lead to droplets forming aerosols as well as fomites,” the group wrote. “Potentially, these droplets could be transmitted beyond 0.5 m although their infectivity could be limited by evaporation.” GP