Long-lasting vision problems following mild cases of COVID-19 may stem from persistent inflammation and nerve damage, even as the results of standard eye examinations appear normal, according to a study today in Nature Communications.
Although less well-known than other long-COVID symptoms, ocular symptoms like pain, light sensitivity, blurred vision, and difficulty reading affect up to 31% to 35% of people with the condition, the study authors note. But this abnormal eye behavior can’t be detected by standard methods, making it difficult for patients to get a diagnosis or treatment.
To better understand the eye problems that develop following a COVID-19 infection, researchers led by a team at Linköping University in Sweden examined 100 people who developed ocular symptoms persisting from three months to three years post-infection. The researchers compared their findings with 32 people who had had COVID-19 but didn’t develop eye symptoms.
Symptoms interfere with daily activities
Roughly 78% of participants had eye symptoms that lasted at least one year, and about 33% of participants had symptoms that lasted at least two years. Symptoms were so significant for a third of participants that they reported taking part- or full-time leave from work. Only 39% of participants had a formal long-COVID diagnosis.
Participants with persistent symptoms experienced a range of ocular abnormalities, including difficulty seeing things up close, eye misalignment, inability to maintain focus, and weakened reflexes in their pupils.
Many participants reported that their symptoms interfered with daily activities, particularly reading printed text or screens. Sensitivity to light was another common symptom. But because these impairments were not detectable in routine exams, it was hard for those with symptoms to get help. “Ocular pathology from SARS-CoV-2 infection…lacks diagnostic criteria and biomarkers, hindering awareness, diagnosis, and medical management,” write the researchers.
The specialized tests used in the study were able to detect changes that conventional exams missed.
Same dysfunctional protein pattern as with fatal COVID
When the researchers analyzed participants’ tear samples, they identified nearly 200 dysregulated proteins linked to immune activity, ocular inflammation, and nerve damage or loss. “Strikingly, the same protein pattern has been found in blood and tissue in cases of severe and fatal COVID in other studies,” notes a Linköping University news release.
Tests of pupillary reflexes showed that the pupils of those with persistent eye symptoms didn’t respond as expected to changes in light or focus. The findings suggest dysfunction in the autonomic nervous system, which controls how pupils respond to stimuli.
Our findings suggest that these people have suffered a severe reaction to COVID-19 manifested in the eyes.
The researchers also found that people with persistent eye symptoms had fewer nerve fibers in the cornea and a weakened blink response, which may indicate nerve damage.
“Our findings suggest that these people have suffered a severe reaction to COVID-19 manifested in the eyes, with long-term inflammation and an impact on the nerves that control multiple eye functions,” says lead author and senior research associate at Linköping University, Petros Moustardas, PhD, in the release.
By identifying the underlying pathologies that give rise to persistent post-COVID eye symptoms, the researchers hope patients will be better able to get diagnosed and treated. They also call for further studies to help an undiagnosed population with quality-of-life-affecting symptoms and disabilities resulting from post-COVID eye syndrome.
