Coronavirus: Does COVID-19 really impact your eyesight - and if so, how?
Boris Johnson and his top aide Dominic Cummings have both suggested that coronavirus may have impacted their eyesight.
Tuesday 26 May 2020 21:10, UK
We know about fevers, persistent coughs and losing your sense of taste, but eyesight has until now not been a major consideration for those who may have contracted coronavirus.
The possibility that COVID-19 may have an affect on eyesight has been in the spotlight after Boris Johnson's chief adviser Dominic Cummings attempted to explain to the nation why he had driven to a local beauty spot during his controversial visit to Durham - which came at the height of the coronavirus lockdown.
Mr Cummings said he was testing his eyesight when he drove from Durham to Barnard Castle on 12 April ahead of a journey back down to London, because he had been experiencing vision issues while suffering from other known symptoms of the illness.
Having backed his top aide, Mr Johnson also later suggested his vision had been affected by COVID-19 as he found himself wearing spectacles "for the first time in years".
But while Mr Johnson may think it's "very, very plausible that eyesight can be a problem associated with coronavirus", what does the science tell us?
Ultimately, there is limited evidence that coronavirus does impact eyesight - but research suggests some patients experience mild ocular symptoms.
The World Health Organisation does include conjunctivitis - which can cause eyes to become itchy and bloodshot - alongside more common symptoms such as a fever and persistent cough, while the UK government does not.
However, it is widely agreed that not enough research has been done to know for certain whether, and to what extent, coronavirus impacts eyesight.
The Royal College of Ophthalmologists has said one of its scientific papers found a few reported cases of viral conjunctivitis among coronavirus patients, but a "lack of evidence" meant it was "unable to report on the association of vision impairment, as a result of a patient contracting COVID-19".
Moorfields Eye Hospital backed this view, saying it could confirm no link between COVID-19 and impaired eyesight.
But professor of ophthalmology at the University of Oxford, Professor Robert MacLaren, said he was confident some people with coronavirus would suffer some eyesight problems.
He pointed to one study of 38 coronavirus patients in the Chinese city of Wuhan - where the virus originated from.
Twelve patients showed symptoms of conjunctivitis, including eyes that were red, swelling, watery and sticky.
When asked about the relatively small subject size, Professor MacLaren insisted it was a "reasonable size" for such a study to "make a prediction based on a larger population".
"It is probably true that there is not any evidence that coronavirus gets into the eye and causes specific problems in a way that other viruses don't," he said.
"But of course there are indirect effects. The question should be: does the virus cause anything different to the eye in a way that the common cold or influenza does not?
"Because any optometrist would tell you, if you're coughing or sneezing, you'll have problems with your vision. But that's not specifically related to the coronavirus - it's the general effects of having a viral illness."
There is of course a difference between symptoms suffered during a bout of coronavirus and sustained visual impairment after recovery.
For the latter, Professor MacLaren highlighted a Brazilian study published in medical journal The Lancet.
The study showed retinal changes - notably spots and small haemorrhages - in 12 adults who had retinal scans during their recovery from COVID-19.
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"If you have thrombosis in the back of your eye, of course that's going to affect your vision," Professor MacLaren said.
"Of course the question is whether or not similar findings would also have occurred if patients had suffered a similarly severe influenza type illness, but caused by another virus."
Professor MacLaren acknowledged the findings were incidental and not clinically significant.
He added that more studies would be needed to determine if there was any sustained visual impairment after coronavirus recovery.