Eye surface changes could identify long COVID

Long COVID could be identified by nerve fibre loss and an increase in dendritic cells on the cornea, doctors suggest today.

The observational study found the changes were seen particularly among those with neurological symptoms, such as loss of taste and smell, headache, dizziness, numbness, and neuropathic pain.

The team, which involved researchers from Necmettin Erbakan University Meram Medical Faculty Hospital, Konya, Turkey, Weill Cornell Medicine-Qatar, Doha, and the Institute of Cardiovascular Sciences at the University of Manchester and NIHR Clinical Research Facility, Manchester, UK, used corneal confocal microscopy (CCM) to pick up nerve damage in the cornea.

CCM has been used to identify nerve damage and inflammatory changes attributable to diabetic neuropathy, multiple sclerosis, and fibromyalgia.

The research involved 40 people who had recovered from confirmed COVID-19 infection between one and six months earlier and they completed a NICE questionnaire, comprising 28 items in nine domains: generalised, respiratory, cardiovascular, neurological, musculoskeletal, psychological/psychiatric, gastrointestinal, dermatological, and ear, nose and throat symptoms, with a score ranging from 0 to 28.

Writing in the British Journal of Ophthalmology, the team says neurological symptoms were present at four and 12 weeks in 22 out of 40 patients (55%) and 13 out of 29 (45%) patients, respectively.

Participants’ corneas were scanned using CCM to look for small nerve fibre damage and the density of dendritic cells, which have a key role in the primary immune system response by capturing and presenting antigens from invading organisms and were compared with those of 30 healthy people who had not had COVID-19.

They found 22 (55%) of the 40 COVID patients had no clinical signs of pneumonia; 11 (28%) had clinical signs of pneumonia not requiring oxygen therapy; four (10%) had been admitted to hospital with pneumonia and received oxygen therapy; and three (8%) with pneumonia had been admitted to the intensive care.

The corneal scans revealed that patients with neurological symptoms four weeks after they had recovered from acute COVID-19 had greater corneal nerve fibre damage and loss, with higher numbers of dendritic cells, than those who had not had COVID-19 infection.

Those without neurological symptoms had comparable numbers of corneal nerve fibres as those who had not been infected with COVID-19, but higher numbers of dendritic cells.

Although this was an observational study with a small number of participants and no long-term monitoring, the researchers write: “To the best of our knowledge, this is the first study reporting corneal nerve loss and an increase in [dendritic cell] density in patients who have recovered from COVID-19, especially in subjects with persisting symptoms consistent with long COVID.”

“We show that patients with long COVID have evidence of small nerve fibre damage which relates to the severity of long COVID and neuropathic as well as musculoskeletal symptoms.”

They say that CCM could be used as a rapid objective ophthalmic test to evaluate patients with long COVID.

Bitirgen G, Korkmaz C, ZAmani A et al. Corneal confocal microscopy identifies corneal nerve fibre loss and increased dendritic cells in patients with long COVID. British Journal of Ophthalmology 27 July 2021; doi 10.1136/bjophthalmol-2021-319450


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