Neurotrophic keratitis (NK) is a condition where the cornea, or clear outer covering of the eye, has reduced sensation due to a variety of reasons. In more advanced cases of NK, the cornea can develop an area of thinning called an ulcer. The purpose of this research is to find out if Oxervate (cenegermin-bkbj 0.002%) an FDA-approved treatment for neurotrophic corneal ulcers leads to an increase in thickness of the corneal stroma (middle layer of the cornea) during and after treatment of a neurotrophic ulcer. Corneal thickness will be measured using optical coherence tomography (OCT), a non-contact imaging device used routinely in ophthalmology examinations. Corneal sensation will also be measured during and after treatment with a device called a Cochet-Bonnet esthesiometer to see if the treatment increases corneal sensation.