Even mild COVID-19 linked to months-long vision problems, Swedish study finds

A study led by researchers at Linköping University in Sweden found that even mild COVID-19 cases can cause vision problems lasting from three months to three years. The research, published in Nature Communications, examined roughly 100 people who had COVID-19 but were not hospitalized. About one-third of participants received partial or full disability reports because of the symptoms, which included severe discomfort, extreme light sensitivity, eye pain and difficulty focusing. Some patients reported trouble reading, studying and continuing work. Standard eye examinations detected no abnormalities, preventing a direct diagnosis. The researchers compared the patients with a control group of 32 COVID-19 patients without symptoms using two specialized tests. The first test identified chronic inflammation and impairment in eye functions controlled by cranial nerves, while the second found that protein patterns in tear fluid were abnormal, resembling those seen in severe and fatal COVID-19 cases. Lead author Professor Neil Lagali said the advanced tests revealed findings missed by standard exams, making the vision problems explainable. The results indicated that virus-related nerve damage disrupts pupil function, allowing excess light into the eye. This was linked to light sensitivity, headaches, difficulty reading and, in some patients, loss of the eyes' ability to work together. The study did not say whether the vision issues are permanent.