In vivo Morphology of Corneal Nerves in Patients With Corneal Allodynia

Abstract

Purpose: : Patients with severe corneal pain, but without obvious clinical signs, are among the most challenging cornea patients. The purpose of this study is to analyze the degree of corneal nerve changes in patients with corneal allodynia by in vivo confocal microscopy (IVCM).

Methods: : A retrospective review of IVCM images was performed for patients referred for IVCM, due to severe unusual corneal pain (n=6), with 4 patients having asymmetric bilateral symptoms. The central cornea of all patients had been imaged bilaterally with a Confoscan 4 IVCM. Three masked observers reviewed the images in regards to morphology and density of the subbasal plexus, including the total number of nerves, number of main nerve trunks, branching pattern, total length of nerves per image, and tortuosity. This data was compared with that of normal control eyes (n=10).

Results: : Patients had a history of dry eye syndrome (n=4 eyes), recurrent erosion syndrome (RES) (n=2 eyes), UV radiation (n=2 eyes), and accutane exposure (n=2 eyes). Total nerve counts (7.4 vs. 13.1), total nerve length (1346 µm vs. 2258 µm), and branching (1.4 vs. 2.1) were significantly (p< 0.01) decreased in eyes with corneal allodynia as compared to normal controls. Changes in main nerve trunks (3.4 vs. 4.7) and tortuosity did not reach statistical significance, although increase in tortuosity was noted in the patient with accutane exposure. Further, tortuosity of deep stromal nerves was noted in the 2 patients with RES.

Conclusions: : IVCM reveals morphological corneal nerve changes in patients with corneal allodynia that may explain their symptoms in the absence clinical corneal signs.

Keywords: imaging/image analysis: clinical • innervation: sensation