Persistent vision issues following mild COVID-19 cases may be linked to ongoing inflammation and nerve damage, even when standard eye exams appear normal, according to recent research published in Nature Communications.
While not as widely discussed as other long COVID symptoms, ocular problems such as pain, light sensitivity, blurred vision, and difficulty reading affect a significant portion of individuals with the condition, impacting up to 31% to 35%. However, these visual disturbances often elude detection through conventional methods, complicating diagnosis and treatment for patients.
To investigate the eye problems that can arise after a COVID-19 infection, a team at Linköping University in Sweden studied 100 individuals experiencing lingering ocular symptoms ranging from three months to three years post-infection. Their findings were compared to a control group of 32 individuals who had COVID-19 but did not develop eye symptoms.
Symptoms Disrupt Daily Life
A substantial majority of participants, around 78%, reported eye symptoms lasting at least a year, with approximately 33% experiencing symptoms for two years or more. For one-third of these individuals, the symptoms were severe enough to necessitate taking time off from work. Formal long COVID diagnoses were held by only 39% of the participants.
Those with persistent symptoms exhibited a variety of ocular abnormalities, including challenges with near vision, eye misalignment, an inability to maintain focus, and reduced pupil reflexes. Many participants found these symptoms significantly interfered with daily tasks, particularly reading printed materials and digital screens. Light sensitivity was another common complaint. The difficulty in obtaining a diagnosis stemmed from the fact that these impairments were not evident during routine eye examinations. As the researchers noted, "Ocular pathology from SARS-CoV-2 infection…lacks diagnostic criteria and biomarkers, hindering awareness, diagnosis, and medical management." The specialized tests employed in the study, however, were capable of identifying changes that standard exams overlooked.
Identical Dysfunctional Protein Signature to Severe COVID
Analysis of tear samples from participants revealed nearly 200 dysregulated proteins associated with immune responses, ocular inflammation, and nerve damage or loss. Notably, "the same protein pattern has been found in blood and tissue in cases of severe and fatal COVID in other studies," according to a Linköping University news release.
Tests assessing pupillary reflexes indicated that individuals with persistent eye symptoms showed abnormal responses to changes in light and focus, suggesting a malfunction in the autonomic nervous system, which regulates pupil behavior.
The researchers also observed a reduction in corneal nerve fibers and a weakened blink response in individuals with persistent eye symptoms, pointing towards 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," stated lead author Petros Moustardas, PhD, a senior research associate at Linköping University.
By pinpointing the underlying biological mechanisms behind persistent post-COVID eye symptoms, the researchers aim to improve diagnostic and treatment pathways for affected patients. They also advocate for further research to identify and support individuals with undiagnosed post-COVID eye syndrome, which can significantly impact quality of life.