U of T and SickKids Surgeons First to Use Nerve Grafts to Restore Sensation in Eye
A team of experts at the University of Toronto and The Hospital for Sick Children (SickKids) have pioneered a novel surgery that restores lost feeling in the eye by transplanting a nerve graft from the patient’s own leg into their eye. This innovative technique, called corneal neurotization, is a new approach to a medical problem that until now had no good solution.
Abby Messner, 18, was the first patient to undergo the surgery in November 2012. She lost feeling her in left eye, a condition called corneal anaesthesia, at the age of 11 after having a brain tumour removed. Because she had no sensation in her left eye, she could not feel pain when the eye was injured or infected. This condition also prevents normal healing from occurring. Without the ability to feel pain, the eye cannot shield itself from elements most people encounter without issue on a daily basis – like dust, microscopic debris and even the wind – so the eye develops scratches, scars and infections that can eventually cause blindness. With potential hazards everywhere, Abby had to quit competitive sports and limit everyday activities like spending time outdoors or walking through the mall with her friends.
“Corneal anaesthesia not only threatens vision, but is also a huge medical, social and economic burden to the patient,” says Professor Asim Ali, an Assistant Professor in the Department of Ophthalmology and Vision Sciences and Staff Surgeon in Ophthalmology and Vision Sciences at SickKids. “Over the years, I have had to watch patients’ eye health progressively decline, offering short-term therapies that could only treat some of the symptoms without addressing the underlying cause. This new technique is the first real opportunity to permanently prevent progression of the disease and may even reverse its effects.”
This new technique would not have been possible without the close collaboration between teams in Ophthalmology and Vision Sciences, and Plastic and Reconstructive Surgery. Professor Gregory Borschel, an Associate Professor in the Division of Plastic and Reconstructive Surgery and U of T’s Institute of Biomaterials and Biomedical Engineering as well as Staff Surgeon in Plastic and Reconstructive Surgery at SickKids, explains how the team applied general nerve regeneration principles to solve this previously-unsolved problem in the eye. The team took part of a nerve from the leg and transplanted it above the eye on the side of the patient’s face that still had feeling. The surgeons then tunneled this nerve graft under the skin across the forehead to the damaged cornea. Under an operating microscope, they separated the nerve into a web of its components, called fascicles, and connected the fascicles to the damaged cornea. Borschel estimates that the cornea then gains sensation over a period of several months, restoring approximately one millimetre of the nerve per day.
“Essentially, we went to a place in the face where there was feeling, and took the nerve input back to the place where there wasn’t,” he says. “The idea is that the nerves will grow across the face from the nerve that is intact to regenerate feeling in the other eye.”
Since Messner’s surgery in 2012, SickKids has treated seven other cases and has been closely studying the outcomes. The procedure has dramatically improved Abby’s quality of life, improved her vision and has made her eligible for a cornea transplant, which would not have been possible without this corneal neurotization technique. The sensation in her left eye was restored within six months.
“Since I was 11 years old, I’ve tried a variety of procedures to keep my eye healthy. It was so unstable that I was back at SickKids every few months. Sometimes I would come in for what I thought would be a straightforward checkup and the next day I’d be in surgery again. It was always a concern that I may lose my vision all together,” says Messner, who is now studying sciences in her first year of university.
Before the development of this new technique, treatment for corneal anaesthesia consisted of increased lubrication with eye drops, injections to the eye to reduce blood vessels (that cause cloudiness in the cornea), wearing a specialized hard contact lens, surgeries to remove scarring, and a procedure called tarsorrhaphy, which is stitching part of the eye closed. Messner has tried them all, but these options only provided temporary relief at best, and brought with them additional lifestyle challenges.
Professor Ronald Zuker of the Department of Surgery at the University of Toronto and Staff Surgeon in Plastic and Reconstructive Surgery at SickKids, explains that another procedure to address corneal anaesthesia has previously been described in medical literature but “it was never clinically adopted because of how invasive it is for the patient.” It involved an incision from ear to ear on the scalp of the patient, and required surgeons to pull down the skin from the patient’s forehead.
The new minimally-invasive technique developed at SickKids involves two small incisions under the eyebrow, which leaves minimal scarring. “It’s a major step forward in the management of children with corneal anaesthesia and for me, a very significant innovation. Our goal is to be able to treat children soon after diagnosis, and stop the problem before any damage is done,” says Ali.
SickKids researchers have published in JAMA Ophthalmology and Plastic and Reconstructive Surgery describing the surgical technique and patient outcomes. The team is now taking this research from the clinical setting back to the SickKids Nerve Regeneration Laboratory headed by Borschel. They are currently studying how the nerve regenerates and the impact of nerve operations on the structure of the brain.
