The role of corneal laser confocal microscopy in the diagnosis of burning eye syndrome and dry eye disease

Relevance Laser confocal microscopy of the cornea (CCM) allows recording morphological changes in corneal nerve fibers (CNF) that occur as a result of excessive evaporation of the tear film, accompanied by the occurrence of chronic neuropathic pain that imitates dryness [1, 2]. Currently, there are no studies on the correlation of morphological changes with complaints, anamnesis, and clinical and functional results in burning eye syndrome (BES) [3–5]. Objective To study structural changes in corneal nerve fibers in patients with burning eye syndrome and dry eye syndrome using laser confocal microscopy and their comparative analysis. Material and methods The study included 54 patients (108 eyes): 17 patients (34 eyes) with a verified diagnosis of dry eye syndrome (Group 1), 17 patients (34 eyes) with mild to moderate dry eye syndrome (Group 2), and 20 volunteers (40 eyes) without identified somatic and ocular diseases (Control Group 3). For objective assessment, all patients were assessed by the number of blinking movements and the completeness of eyelid closure, the Norn test, and the Schirmer I test were performed. For objective assessment of NVR, a Heidelberg Retina Tomograph III laser confocal microscope with a corneal module (Heidelberg Engineering GmbH, Germany) was used. Results According to the CMR data, patients with FGS had larger microneuromas than patients with DES, and the lowest values ​​of the anisotropy coefficient of the directionality of the corneal nerve fibers (2.605), indicating the greatest changes in the structure of the nerve fiber. However, no reliable correlation was found in the group of patients with FGS between the value of the Norn test, the number of blinks, and the KΔL value of the NVR (r = -0.45, p = 0.07 and r = -0.45, p = 0.07). Conclusion A comparative analysis of the state of the NVR in FGS and DES revealed statistically significant differences in the structure of the fibers, including their tortuosity, as well as the presence of microneuromas in 100% of cases with FGS. The laser CMR method has great diagnostic value in identifying changes in the NVR associated with the development of neuropathic pain syndrome. Key words: corneal confocal microscopy; corneal nerve fibers; corneal nerve fiber changes; burning eye syndrome; dry eye syndrome