American Society for Peripheral Nerve

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An Evaluation of the Effect of Corneal Neurotization on Corneal Epithelial Thickness in a Rat Model of Neurotrophic Keratopathy
Kira Antonyshyn, BSc1,2; Joseph Catapano, MD, PhD1; Jennifer J Zhang, MD, PhD1; Tessa Gordon, PhD3; Gregory H. Borschel, MD, FAAP, FACS4
1The Hospital for Sick Children, Toronto, ON, Canada, 2University of Toronto, Toronto, ON, Canada, 3Neurosurgery/Spine Center, The Hospital for Sick Children, Toronto, ON, Canada, 4Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, ON, Canada

Introduction:
Neurotrophic keratopathy (NK) develops in the absence of corneal sensory innervation, and results in corneal epithelial ulcerations that can lead to progressive scarring and vision loss. Corneal neurotization is a novel surgical procedure that restores sensory innervation in patients with NK (Elbaz et al. 2014). In our rat model of NK, we demonstrated neurotization decreases the incidence of corneal ulcerations and improves the rate of healing. The epithelium is normally thicker in the central versus peripheral cornea, and central corneal epithelial thinning accompanies corneal denervation. Here, we investigate the effect of treatment with corneal neurotization on the thickness of the corneal epithelium and stroma in our rat model of NK.

Materials and Methods:
Three conditions were assessed: NK, NK with corneal neurotization, and normal intact corneal innervation. The affected corneas were harvested four and five weeks after corneal denervation without and with treatment with corneal neurotization, respectively. Corneas were cut into 8Ám sections. Four sections from each cornea, sampled from representative areas of peripheral and central cornea, were analyzed. Sections were stained with Hematoxylin and Eosin. Using ImagePro, each section was imaged at 200X magnification, and epithelial and stromal thicknesses in the central and peripheral cornea of each section were evaluated. Mean thicknesses were compared using an unpaired t-test.

Results:
In the neurotized cornea, four days after corneal ulceration had recovered, there was a significantly thicker central as compared to peripheral corneal epithelium (p=0.028). The central epithelium in this group was significantly thicker than in the NK cornea (p=0.014). There was no difference in the thickness of the central epithelium in the normally innervated compared to the NK and treated corneas. There was no significant difference between the central and peripheral epithelial thickness in the NK cornea, as well as, unexpectedly, in the normally innervated cornea. There was no difference in the peripheral corneal epithelial thicknesses, nor in the central or peripheral stromal thicknesses between the three groups.

Conclusions:
In rats with NK, treatment with cornea neurotization increased corneal epithelial thickness, suggesting that the healing process was ongoing at the time of corneal harvest, despite superficial recovery from a previous ulcer. Our previous healing and ulceration experiments implicate corneal reinnervation in this process. Further studies with larger sample sizes are being conducted to elucidate the changes in epithelial thickness that occur throughout corneal healing over time in the three groups.


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