The study, published in the British Journal of Ophthalmology, said through an eye scan, doctors can identify increased nerve fiber loss and increased immune cells which they say appears in individuals suffering from long COVID.
Researchers involved with the study define long COVID as the continuation of symptoms for four weeks beyond the time in which the inflammatory response phase of the infection has passed. Around one out of 10 people who contract COVID-19 suffer from these long-term symptoms.
“I think this is important for two reasons,” Rayaz A. Malik, the lead author of the study, told Newsweek. “One is to help treating physicians to actually do a test to be able to say, well, yes or no (this person has long COVID). And equally, from a practitioner’s point of view, there are people who will have symptoms but may not have underlying pathology.”
The study was conducted through the administering of a National Institute of Health and Clinical Excellence (NICE) questionnaire where participants’ answers were processed to determine if they suffered from long COVID.
Those who met the diagnosis were then given a corneal confocal microscopy (CCM) scan to identify small nerve damage and the presence of immune cells, known as dendritic cells, which play a role in the body’s immune system response.
Researchers then compared these scans with those of 30 people who had not contracted COVID-19. The results showed long COVID sufferers had increased nerve fiber loss and increased dendritic cells compared to those who had not contracted the virus. Those with long COVID symptoms had similar numbers of nerve fibers to people who had recovered from COVID, yet those without long COVID symptoms had higher numbers of dendritic cells.
This is not the first time CCM scans have served a role in determining nerve damage and inflammatory changes. The same technology has been used in the analysis of those diagnosed with diabetic neuropathy, multiple sclerosis, and fibromyalgia.
In regard to the findings presented in this study, BMJ Journals, which publishes the British Journal of Ophthalmology, said the study did have some limitations.
“This is an observational study, and as such, can’t establish cause,” BMJ Journals said in a statement. “The researchers also acknowledge several limitations, including the relatively small number of study participants. the absence of longer-term monitoring, and reliance on questionnaires to establish the severity of neurological symptoms rather than more objective measures.”
The statement added that the results may have some clinical applications. “Corneal confocal microscopy may have clinical utility as a rapid objective ophthalmic test to evaluate patients with long COVID,” it said.
Update - 7/28/21 4:25 PM - This story has been updated with comments from Rayaz A. Malik.
