The use of enlarged breath shields has been suggested as part of a wide range of infection control measures implemented during the COVID-19 pandemic. Breath shields have long been a standard feature of slit lamps and act as a physical barrier between the examiner and subject but there is an absence of evidence on their effectiveness in reducing droplet transmission and respiratory infections.

SARS-CoV-2 shares many of the features of other respiratory viruses including SARS-CoV-1 and is thought to be commonly spread though respiratory droplets (>5 μm) and fomites [1]. Fomites are formed either from droplets settling on surfaces or through direct contamination from touching mucosal surfaces. Smaller aerosolised droplet nuclei (≤5 μm) can travel further and remain in air longer. They have been shown to carry viable virus particles in experimental conditions [2] but are not thought to be a common mode of transmission of COVID-19 [1]. The risk of transmission from tears is also thought to be low [3].

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