A new study published in Nature Communications found that 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.” CIDRAP has the news.

Ocular symptoms like “pain, light sensitivity, blurred vision, and difficulty reading affect up to 31% to 35% of people with the condition.” Patients have found it difficult to get treatment because the results aren’t detected by standard methods.

Roughly 78% of study 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 experienced a range of symptoms, including “difficulty seeing things up close, eye misalignment, inability to maintain focus, and weakened reflexes in their pupils.”

When the researchers analyzed participants’ tear samples, “they identified nearly 200 dysregulated proteins linked to immune activity, ocular inflammation, and nerve damage or loss.” The same protein pattern has been found in blood and tissue in “cases of severe and fatal COVID in other studies.” People with symptoms also had “fewer nerve fibers in the cornea and a weakened blink response, which may indicate nerve damage.”