Diagnosing neuropathic corneal pain can be challenging, as it is often difficult to differentiate from conventional dry eye disease (DED). Researchers recently found that in vivo confocal microscopy (IVCM) may be used as an adjunct tool for the diagnosis of neuropathic pain in the presence of neuropathic symptoms, with microneuromas potentially serving as a diagnostic biomarker.

This comparative, retrospective, case-control study included 25 neuropathic pain patients, 30 DED patients and 16 age- and sex-matched healthy controls. All participants underwent corneal imaging with IVCM, and the researchers analyzed the results for nerve density and number, presence of microneuromas, nerve beading and dendritiform cell density.

The team observed a decrease in total nerve density in both neuropathic pain (14.14±1.03mm/mm2) and DED patients (12.86±1.04mm/mm2) compared with normal controls (23.90±0.92mm/mm2). However, they noted that neither the total nerve density nor the presence of nerve beading was statistically different between neuropathic pain and DED patients.

In all patients with neuropathic corneal pain, the investigators discovered microneuromas, which were not present in any of the patients with DED. They noted that dendritiform cell density was increased significantly in both neuropathic corneal pain (71.89±16.91cells/mm2) and DED patients (111.5±23.86cells/mm2) compared with normal controls (24.81±4.48cells/mm). However, they added that there was no significant difference in dendritiform cell density between DED and neuropathic pain patients.

Moein HR, Akhlaq A, Dieckmann G, et al. Visualization of micro-neuromas by using in vivo confocal microscopy: an objective biomarker for the diagnosis of neuropathic corneal pain? Ocul Surf. July 11, 2020. [Epub ahead of print].