Neurotrophic cornea results from a trigeminal neuropathy that causes decreased corneal innervation and sensation. Corneal innervation is critical for the maintenance of corneal epithelial and limbal stem cell health and function. An insensate cornea can lead to poor corneal wound healing, chronic corneal abrasion or ulceration, and ultimately perforation and/or scarring. In severe cases, permanent vision loss can occur.
Current established therapies for neurotrophic cornea — including frequent lubrication, special protective contact lenses, tarsorrhaphy, and corneal gluing — are temporizing and do not restore vision.
What is corneal neurotization?
Neurotization is a well-established technique involving the transfer of healthy donor nerve into a tissue to re-establish motor or sensory innervation. Neurotization to an insensate cornea offers a new potential treatment and cure for neurotrophic cornea.
Corneal neurotization was first successfully described using a direct transfer of the contralateral supratrochlear and supraorbital nerves to the limbal area of an affected cornea using a bi-coronal surgical approach. Since then, several modifications have been described, including the use of a sural nerve grafted to the contralateral supratrochlear nerve with attachment of the nerve graft fascicles to the sclera at the corneal limbus. This approach is less invasive, requiring only small eyelid incisions.
Treating neurotrophic cornea in children
The management of neurotrophic cornea in children can be especially challenging. Corneal anesthesia may be difficult to diagnose in very young children. Office corneal examinations can be limited, requiring sedation or general anesthesia. Frequent lubrication to prevent corneal breakdown can be challenging for families to implement. Tarsorrhaphy is disfiguring and potentially amblyogenic. Corneal neurotization is an especially exciting potential treatment option and cure for young patients with neurotrophic cornea.
At Children's Hospital of Philadelphia (CHOP), we have now performed the sural nerve graft procedure on 3 children (ages 6, 7, and 8 years old) with neurotrophic cornea and a history of corneal ulceration, scarring, and tarsorrhaphy. The oculoplastics and plastic surgery teams work together to perform this 4-hour operation.
About the sural nerve graft procedure
Briefly, the median cutaneous branch of the sural nerve is harvested from the leg. The contralateral supratrochlear nerve is isolated through a small upper eyelid incision. The nerve graft is tunneled across the nasal bridge and into the subconjunctival space on the affected side.
Distally, the epineurium is dissected away and individual nerve fascicles are isolated.
At 4 sites around the corneal limbus, the conjunctiva and tenon’s capsule are opened to expose bare sclera. Individual nerve fascicles are secured at each of these sites. Conjunctiva is closed.
Proximally, the graft is coapted to the supratrochlear nerve. A temporary medial and lateral suture tarsorrhaphy are placed to protect the ocular surface during healing.
The procedure has been well tolerated and without complications. There is an expected small patch of numbness on the back of the leg from sural nerve graft harvesting. We have found a return of corneal sensation as early as 2 months after using this groundbreaking technique. Perhaps even more meaningful has been the improvement in corneal appearance among eyes treated with this surgery. There has been a reduction in corneal scar density and improvement in corneal health, allowing for the reversal of previously placed permanent tarsorrhaphies. Using in vivo confocal microscopy, we have also been able to show an increase in corneal nerve density following the procedure.
We hope to continue to perform this procedure in children with neurotrophic cornea and resulting corneal sequela, such as frequent abrasions, ulcers, and scarring. We also hope to continue to develop improved ways of objectively measuring postoperative improvement in corneal sensation among children.
Reference: Elbaz U, Bains R, Zuker R, Borschel G, Al A. Restoration of corneal sensation with regional nerve transfers and nerve grafts: a new approach to a difficult problem. JAMA Ophthalmol. 2014;132(11):1289-1295.