The cornea – the clear part in the front of the eye – is a unique biological tissue in that it has no blood vessels and is optically clear. The clarity of the cornea is a fundamental aspect of vision; without this clarity, good vision is impossible.
While the cornea lacks blood vessels and mostly obtains its oxygen supply directly from the air, it is very rich in innervation. It is among the most highly innervated tissues in the body, and even minor injuries to the cornea can be terribly painful (e.g. corneal scratch). Fortunately, the cornea is also the fastest healing tissue in the body. The ability of the cornea to heal requires special biological signals from the nerves. This signals – neurotrophic molecules – stimulate the cells of the cornea to divide and reform the damaged tissue.
Neurotrophic keratitis is a disorder in which the cornea has lost its nerves. There are many causes to neurotrophic keratitis, including chronic trauma from dry eyes, chronic inflammation, herpes infection, and even congenital absence of the nerve.
A major medical advance of the past decade has been the development of techniques to reinnervate the cornea. These include both medical (eye drops) and surgical (corneal neurotization). The eye drops (cenegermin-bkbj, known as Oxervate) are most useful when the denervation is distal and fairly recent, caused by chronic dry eyes. Otherwise, surgery is required.