Researchers in India sampled 304 coronavirus patients at a hospital in Kanpur Dehat, Uttar Pradesh, and found 58 of them (19 per cent) consistently wore spectacles during the daytime.

Comparing the proportion to data on glasses-wearing from the wider population, they estimated the group was 2.8 times less likely to become infected.

The study’s author, Amit Kumar Saxena, an ophthalmologist from India’s National Programme for Control of Blindness, suggested ‘repeated touching and rubbing of the eyes’ could be a ‘significant route’ of transmission.

He said the virus could be passed from fluids protecting the eye to the upper throat via the tear duct.

The research has yet to be peer-reviewed and was based on patients’ self-reported use of glasses rather than clinical observations.

The author stressed the sample size of patients was ‘small’ and studied over a short period.

He also said it was difficult to control for socioeconomic factors, suggesting non-glasses-wearers were more likely to be from less-well off or less-educated backgrounds who were at greater risk of infection for unrelated reasons.

The findings may be skewed by the study’s small sample size and confounding social factors

These factors may affect behaviour differently around the world.

The patients were all aged between 10 and 80 and none were severely ill.

Researchers found they touched their face up to 23 times each hour on average and there eyes three times.