NEW YORK — “Long COVID” continues to confound doctors as patients still struggle with debilitating symptoms months after first being infection. A new study now suggests that COVID patients who could be long-haulers could be diagnosed by taking a close look at their eyes. Nerve fiber loss and an increase in key immune cells on the surface of the eye may be a way of identifying the long term impact of the virus, say scientists.
The changes are particularly evident among those with neurological symptoms, such as loss of taste and smell, headache, dizziness, numbness, and neuropathic pain. Doctors at Weill Cornell Medicine-Qatar say long COVID is characterized by a range of symptoms which continue for more than four weeks after the acute phase of the infection has passed, and which aren’t explained by an alternative diagnosis.
Around one in 10 people infected by the virus will become COVID long-haulers. It has been suggested that small nerve fiber damage may underlie its development.
To explore the theory, researchers used a real-time, non-invasive, high-resolution imaging laser technique, called corneal confocal microscopy — or CCM — to pick up nerve damage in the cornea. The cornea is the transparent part of the eye that covers the pupil, iris, and the fluid-filled interior. Its main function is to focus most of the light entering the eye.
CCM has been used to identify nerve damage and inflammatory changes attributable to diabetic neuropathy, multiple sclerosis, and fibromyalgia..
Forty people who had recovered from confirmed COVID-19 infection between one and six months earlier completed a National Institute of Health and Clinical Excellence (NICE) questionnaire. Data was used to find out if they had long Covid, with a total score ranging from zero to 28. Neurological symptoms were present at four and 12 weeks in 22 out of 40 patients (55 percent) and 13 out of 29 (45 percent), respectively, according to the findings published in the British Journal of Ophthalmology.
The participants’ corneas were then scanned using CCM to look for small nerve fiber damage and the density of dendritic cells. These have a key role in the primary immune system response by capturing and presenting antigens from invading organisms.
The corneal scans were compared with those of 30 healthy people who hadn’t been infected by COVID.
Results show that 55 percent of the COVID patients had no clinical signs of pneumonia. Twenty-eight percent had clinical signs of pneumonia not requiring oxygen therapy. Ten percent had been admitted to hospital with pneumonia and received oxygen therapy, and 8 percentt with pneumonia had been admitted to the intensive care.
The corneal scans revealed that patients with neurological symptoms for four weeks after they had recovered from acute COVID-19 had greater corneal nerve fiber damage and loss, with higher numbers of dendritic cells, than those who hadn’t been infected by the virus. Those without neurological symptoms had comparable numbers of corneal nerve fibers as those who hadn’t been infected with COVID, but higher numbers of dendritic cells.
He notes that it was an observational study, and as such, can’t establish cause, and only a small number of participants were involved.
“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,” he adds. “We show that patients with long COVID have evidence of small nerve fiber damage which relates to the severity of long COVID and neuropathic as well as musculoskeletal symptoms. Corneal confocal microscopy may have clinical utility as a rapid objective ophthalmic test to evaluate patients with long COVID.”
South West News Service writer Stephen Beech contributed to this report.