Corneal Nerve and Epithelial Cell Alterations in Corneal Allodynia: An In Vivo Confocal Microscopy Case Series

Abstract Purpose To investigate the morphological changes of the corneal epithelium and sub-basal nerves in patients with corneal allodynia using in vivo confocal microscopy (IVCM). Design Case-control study of patients with corneal allodynia and healthy controls. Methods Ten eyes of six patients were diagnosed with corneal allodynia at a single center and compared to fifteen healthy eyes. IVCM of the central cornea was performed on all subjects and controls. Images were retrospectively analyzed for number of corneal subbasal nerve main trunks and branches, total nerve length, tortuosity, corneal superficial and basal epithelial cell density and superficial epithelial cell size. Results Corneal allodynia was seen in patients with dry eye disease, recurrent erosion syndrome, exposure to ultraviolet radiation, and accutane use. Compared to controls, patients with corneal allodynia had a significant decrease in the total numbers of sub-basal nerves (p=0.02), nerve branches (p=0.006), total nerve length (p=0.009), total nerve density (p=0.009) and superficial and basal epithelial cell densities (p