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Corneal Nerve and Epithelial Cell Alterations in Corneal Allodynia: An In Vivo Confocal Microscopy Case Series
Pedram Hamrah1, Yureeda Qazi2, Bashar Shahatit2
1Boston Image Reading Center, New England Eye Center, Department of Ophthalmology, Tufts Medical Center, Tufts University School of Medicine, Boston, MA, USA; Cornea Service, New England Eye Center, Department of Ophthalmology, Tufts Medical Center, Tufts University School of Medicine, Boston, MA, USA; Ocular Surface Imaging Center, Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, MA, USA; Cornea & Refractive Surgery Service, Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, MA, USA.
Purpose:
To investigate morphological changes of the corneal epithelium and subbasal 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 numbers of total corneal subbasal nerves, main trunks and branches, total nerve length and density, nerve branching, and tortuosity, superficial and basal epithelial cell densities, and superficial epithelial cell size.
Results:
Corneal allodynia was seen in patients with dry eye disease, recurrent corneal 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 subbasal nerves (P=.014), nerve branches (P=.006), total nerve length (P=.0029), total nerve density (P=.0029) and superficial and basal epithelial cell densities (P=.0004, P=.0036) with an increase in superficial epithelial cell size (P=.016). There were no statistically significant differences in the number of subbasal nerve main trunks (P=.09), nerve branching (P=.21), and nerve tortuosity (P=.05).
Conclusions:
Corneal IVCM enables near-histological visualization and quantification of the cellular and neural changes in corneal allodynia. Regardless of etiology, corneal allodynia is associated with decreased corneal epithelial cell densities, increased epithelial cell size, and decreased numbers and lengths of subbasal nerves despite an unremarkable slit-lamp examination. Therefore, IVCM may be useful in the management of patients with corneal allodynia.
