Laser confocal microscopy of corneal nerve fibers in patients with burning eye syndrome and dry eye disease

Abstract

Background. Excessive evaporation of the tear film can lead to damage to the corneal nerve fibers and cause the occurrence of chronic neuropathic pain that mimics dryness. Laser confocal microscopy of the cornea allows you to record morphological changes in the nerve fibers of the cornea and can be a diagnostic tool for finding the substrate of neuropathic pain.Aim. To study and compare the structural changes of corneal nerve fibers in patients with burning eye syndrome and dry eye disease.Materials and methods. 54 patients (108 eyes) aged 20–35 years were examined: 17 patients (34 eyes) with a verified diagnosis of mild and moderate dry eye disease were the first group, 17 patients (34 eyes) with burning eye syndrome were the second group. The third group (control) consisted of 20 volunteers (40 eyes) of the same age, who did not have any somatic and eye diseases. The criterion for exclusion from the study was the presence of clinical signs of blepharitis and dysfunction of the meibomian glands in patients and individuals of the control group. In all patients, the number of blinking movements and the completeness of eyelid closure were determined, the Norn test and the Schirmer I test were performed. For an objective assessment of corneal nerve fibers, laser confocal microscopy of the cornea was used on a Heidelberg Retina Tomograph III device with a rostock corneal module.Results. The lowest values of the anisotropy coefficient of the corneal nerve fibers directivity were recorded in the group of patients with burning eye syndrome (2.605), which indicates the greatest changes in the structure of the nerve fiber in this group. There was no significant negative correlation between the value of the Norn sample, the number of blinking movements, and the value of the anisotropy coefficient of the corneal nerve fibers orientation in the group of patients with burning eye syndrome (r = –0.45, p = 0.07 and r = –0.45, p = 0.07). There was a statistically significant (p >0.05) increase in the number of inflammatory Langerhans cells, the length and density of their processes in the groups of burning eye syndrome and dry eye disease compared with the group of healthy volunteers.Conclusion. The method of laser confocal microscopy of the cornea can be used to detect changes in corneal nerve fibers associated with the occurrence of neuropathic pain syndrome.