Longitudinal Morphometric Analysis of Sub-Basal Nerve Plexus in Contralateral Eyes of Patients with Unilateral Neurotrophic Keratitis

Abstract

Objectives: To investigate longitudinally corneal sub-basal nerve plexus (SNP) by means of in vivo confocal microscopy (IVCM) in the contralateral eye (CE) of patients with unilateral neurotrophic keratitis (NK) secondary to central nervous system (CNS) diseases who underwent different treatments. Methods: Ten patients with NK and 10 matched controls were included. In 7 NK patients, conservative treatment maintained unchanged the clinical picture over the 1-year follow-up (Group 1), while NK progressed in 3 patients who underwent direct corneal neurotization (Group 2). IVCM scans of SNP of NK patients were acquired in CE at baseline (V0) ad after 1-year follow-up (V1). All images were analyzed with the automated software "ACCMetrics" and compared with controls. The following IVCM corneal nerve parameters were calculated at V0 and V1 with ACCMetrics: fiber density (CNFD), branch density (CNBD), fiber length (CNFL), total branch density (CTBD), fiber area (CNFA), fiber width (CNFW), and fractal dimension (CNFrD). Results: At V0, significantly lower mean values of CNFD and CNBD, and higher values of CNFW were detected in CE of NK patients compared to controls (respectively, 16.9 ± 8.7 vs 25.0 ± 8.3 n/mm², P= .029; 19.3 ± 13.8 vs 33.8 ± 18.9 n/mm², P= .023; 0.022 ± 0.002 vs 0.020 ± 0.001 mm/mm², P< .001). From V0 to V1, all IVCM metrics of CE remained unchanged in Group 1, while they improved in Group 2. Conclusions: Contralateral eye of patients with unilateral NK secondary to CNS disease showed lower CNFD and CNBD and higher CNFW compared to controls. Unlike conservative treatment, direct corneal neurotization was able to improve SNP metrics also in CE.

Keywords: In vivo confocal microscopy; contralateral eye; corneal neurotization; neurotrophic keratitis; sub-basal nerve plexus.