Despite being successful, corneal neurotization — a surgical procedure that seeks to restore nerve function in the cornea — does not guarantee neurotrophic keratitis (NK) patients will fully regain their vision and no longer need corrective lenses.
Researchers who made that finding also noted that future studies should focus on assessing the effectiveness of topical treatments like Oxervate (cenegermin), alone and in combination with corneal neurotization, to promote cornea healing.
These recommendations were detailed in the article “Corneal Neurotization for Trigeminal Anesthesia,” published in Bulletin, the official magazine of the American Academy of Otaloryngology-Head and Neck Surgery.
NK is a degenerative eye disease in which the nerves serving the cornea — the transparent outer layer of the eye that controls the entry and focus of light — are progressively damaged. When these nerves malfunction, the cornea loses sensitivity and its ability to self-repair and starts to break down, leading to vision loss.
The disease may be triggered by damage to the trigeminal nerve — a large and complex nerve that controls tear production, along with facial movement and sensation. Such damage may occur after patients undergo brain surgery to remove certain tumors.
Damage to the trigeminal nerve also may impair its ability to produce and release neurotrophic factors — proteins and other molecules that promote nerve cell development and survival. Those proteins are needed for the growth, maturation, and survival of corneal nerves.
Thus, “even in the absence of mechanical trauma, loss of neurotrophic support to the ocular [eye] surface results in morphologic and metabolic disturbances that may impair vision,” the authors wrote.
Treatments to manage NK usually focus on promoting healing the cornea, either by using topical medications containing neurotrophic factors like Oxervate, or having patients wear bandage contact lenses, or have surgery to partially close their eyelids, to protect their cornea. Despite being able to halt NK progression, none of these treatments addresses its underlying cause.
More recently, it has been found that corneal neurotization, a surgical procedure in which healthy nerves from another part of the body are transplanted into the cornea to restore corneal nerve function, may help restore corneal sensitivity, improve vision, and potentially cure NK.
According to study authors, this surgical procedure may be particularly beneficial to patients with severe cornea damage, “wherein the goal is to render them candidates for second-stage corneal transplant to help restore their vision.”
Despite its promising potential, corneal neurotization also carries the risk of vision loss. According to the authors, the most important factors influencing the surgery’s success include the surgeon’s experience, the patient’s ability to promote the healing of transplanted nerves, and certain aspects of the disease itself.
“In our opinion, the procedure is optimally performed in a team approach comprising specialists in corneal and cranial nerve surgery,” they wrote, adding that processed human nerves sometimes used to surgically repair gaps in other nerves in the body should not be used in corneal neurotization, as they tend to be less effective than those harvested from patients.
They also noted that patients undergoing the procedure should “be aware that successful corneal neurotization does not guarantee improved vision and that corrective lenses may still be needed after surgery to maximize vision and protect the cornea.”
The researchers continued: “As corneal healing following neurotization in NK is believed to result from restoration of neurotrophic support to the ocular surface, future research should seek to compare the effectiveness of topical recombinant [man-made] trophic factors alone (i.e., Cenegermin) or in combination with corneal neurotization procedures.”