2007 OMIG, Abstract 23

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In Vivo Morphology of Corneal Nerves and Corneal Sensation in Herpes Simplex Keratitis
Pedram Hamrah, MD : Mohammad H. Dastjerdi, MD,  Reza Dana, MD, MPH, MSc, Deborah Pavan-Langston, MD
Cornea Service, Massachusetts Eye & Ear Infirmary, Dept of Ophthalmology, Harvard Medical School

Purpose: Neurotrophic keratopathy is thought to result from loss of corneal sensation due to denervation, with most cases caused by herpes simplex keratitis (HSK). The purpose of this study is to correlate the degree of corneal nerve alterations and morphology in HSK by in vivo confocal microscopy with results of corneal sensation.
Methods: A prospective study was performed in patients with HSK (n=33). The corneal sensation was measured in both the affected and contralateral eyes, as well as in 10 normal eyes of 5 subjects with a Cochet-Bonnet esthesiometer. HSK patients were grouped into normal (sensation >5.5 cm), mild (>2.5 cm to <5.5cm) and severe (<2.5 cm) loss of corneal sensation. The central cornea of all normal subjects and patients with HSK were imaged bilaterally with a Confoscan 4 confocal microscope (Nidek Technologies). Two masked observers reviewed the confocal images in regards to corneal nerve morphology 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.
Results: There was a significant (p< 0.003) decrease in total nerve count, main trunks, and total nerve length in HSK eyes, which correlated strongly with corneal sensation in all subgroups (p<0.001). Branching and tortuosity were decreased in HSK eyes, although they did not achieve statistical significance. Alterations in nerve morphology were noted within days of acute disease. Surprisingly, contralateral eyes in HSK patients also demonstrated a decrease in total nerve length, total nerve number, and main nerve trunks without signs of clinical disease.
Conclusions: Corneal nerve alterations in the affected eyes correlate highly with the loss of corneal sensation. Confocal microscopy reveals a bilateral loss of the subbasal nerve plexus, starting immediately after HSV infection.  In vivo confocal microscopy enables a direct comparison of corneal sensory innervation and sensitivity.

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