A study led by an Indian-origin scientist shows that sore eyes are the most important vision-based indicator of Covid-19, thereby providing more information about the virus and its movement through the body.

Researchers at Anglia Ruskin University (ARU) in the United Kingdom prepared a questionnaire for people who have contracted coronavirus and asked them to detail their symptoms while comparing it to their condition before the diagnosis.

“This is the first study to investigate the various eye symptoms indicative of conjunctivitis in relation to Covid-19, their time frame in relation to other well-known Covid-19 symptoms and their duration,” Professor Shahina Pardhan, Director of the Vision and Eye Research Institute at ARU and the lead author of the study, said.

Published in the journal BMJ Open Ophthalmology, the study shows that sore eyes were significantly common among participants who tested positive, with 16 per cent reporting the problem as one of the symptoms.

“Just 5 per cent of the participants reported having had the condition beforehand,” the researchers said.

“While 18 per cent of people reported suffering from photophobia or light sensitivity as one of their symptoms, this was only a 5 per cent increase from their pre-coronavirus state”, they added.

Out of the 83 per cent respondents, 81 per cent said they had issues with the eyes emerging within two weeks of other Covid-19 symptoms, while out of that, 80 per cent reported that it lasted for less than two weeks.

The most common reported symptoms overall were fatigue, suffered by 90 per cent of respondents, a fever was seen among 76 per cent and a dry cough was reported by 66 per cent.

“While it is important that ocular symptoms are included in the list of possible Covid-19 symptoms, we argue that sore eyes should replace 'conjunctivitis' as it is important to differentiate from symptoms of other types of infections, such as bacterial infections, which manifest as mucous discharge or gritty eyes,” Pardhan said.

“This study is important because it helps us understand more about how Covid-19 can infect the conjunctiva and how this then allows the virus to spread through the body,” she added.