COVID's hidden eye effects come into focus

Clinical takeaway: Consider referral to ophthalmology or neuro-ophthalmology for patients with persistent light sensitivity, eye pain, reading difficulty, or focusing problems after COVID-19 despite a normal routine eye examination. Standard eye exams may miss objective abnormalities detectable with specialized testing.

Many patients with long COVID report persistent visual symptoms, but routine eye examinations often fail to identify an underlying cause. This study suggests that a distinct post-COVID eye syndrome involving chronic inflammation and nerve dysfunction may explain these otherwise unexplained symptoms.

Researchers evaluated 100 adults with persistent ocular symptoms lasting three months to three years after non-hospitalized COVID-19 and compared them with 32 adults who had recovered from mild COVID-19 without eye symptoms. One-third of affected participants were on full- or part-time sick leave because of their symptoms.

Standard ophthalmic examinations were largely normal. However, specialized testing identified abnormalities in multiple eye functions, including reduced corneal nerve density, increased inflammatory immune cells in the cornea, impaired pupillary light reflexes that allowed excess light into the eye, and subtle eye-muscle coordination deficits affecting near vision. These findings were consistent with patients' reports of photophobia, eye pain, headaches, eye fatigue, and difficulty reading or maintaining focus.

Analysis of tear fluid also identified protein patterns associated with immune dysregulation and nerve injury that resembled those reported in severe COVID-19. Using these clinical findings, investigators developed diagnostic models that identified affected patients with 77% accuracy using specialized eye tests alone and 91% accuracy when tear protein biomarkers were added.

Although the study does not establish how common this syndrome is or how best to treat it, it provides objective evidence that persistent post-COVID eye symptoms can have an identifiable biological basis even when routine eye examinations are normal.

"These people are really struggling in their daily lives. Now we know what's wrong with their eyes, and have several clues as to how COVID-19 may have caused these problems. We hope that the findings can lead to effective treatment and that in the long run their problems will ease, but unfortunately we don't know yet," said senior study author Neil Lagali, professor of experimental ophthalmology at Linköping University.

Source: Moustardas P, et al. (2026 July 8) Nat Commun. Long-term ocular symptoms following COVID-19 linked to immune dysregulation, dysautonomia and peripheral neuropathy