Scientists have warned that even a mild case of COVID-19 could lead to vision problems that last for months or even years, adding a new effect to the list of long-term complications of the virus.
The study, led by researchers from Sweden’s Linköping University and published in the journal Nature Communications, included about 100 people who had COVID-19 and did not require hospitalization, but suffered from vision problems that lasted between 3 months and 3 years.
One-third of the participants were on sick leave, either full or partial, due to symptoms.
Those affected described suffering from severe discomfort, extreme sensitivity to light, sharp eye pain, and difficulty focusing their vision, to the point that some were no longer able to read texts, which prevented them from continuing to study or work.
Interestingly, traditional eye examinations did not reveal any abnormalities, leaving doctors unable to provide a diagnosis or explanation for the symptoms.
To solve this puzzle, the team compared the condition of these patients with a control group of 32 people who also had COVID-19 but without showing visual problems.
The researchers then resorted to two specialized tests. The first revealed chronic inflammation and deterioration in multiple eye functions controlled by brain nerves, while the second, which analyzed proteins in tear fluid, showed an abnormal pattern of proteins regulating nerves and immunity, similar to what is seen in severe and fatal cases of COVID-19.
The study's lead author, Professor Neil Lagaley, explained that these advanced tests revealed what ordinary examinations failed to see, confirming that the visual problems of those affected are now explainable.
It was found that nerve damage caused by the virus led to pupil dysfunction, allowing excessive light to enter the eye. This explains the extreme light sensitivity reported by patients, as well as the headaches, difficulty reading, and trouble concentrating. The nerve damage was also linked to the development of strabismus (crossed eyes) in some individuals, where the eyes lose their ability to coordinate.
The researchers hope their findings will be more widely generalized, acknowledging that their study involved only a small sample of Swedes. They aspire for this discovery to lead to the development of effective treatments, but recognize that there is still a long way to go to understand how to alleviate this ongoing suffering.
