Surgeons at Toronto's Hospital for Sick Children have developed a procedure that could prevent blindness in patients with corneal anesthesia, a serious but rare disease.

But they never imagined their treatment could be used to treat thousands of patients worldwide with long forgotten diseases like leprosy.

A team of two plastic surgeons and one ophthalmologist at Sick Kids has developed a new nerve graft procedure that could return feeling to eyes that have lost all ability to sense pain.

It was supposed to be a highly specialized surgery that would only be used in a small number of kids in Toronto. But to everyone's surprise it quickly piqued the interest of surgeons in India, Colombia, Argentina, France, China and around the world.

"There's a big pent-up demand for adults. There's a huge number of people that could benefit," says Dr. Asim Ali, who developed the procedure along with Dr. Gregory Borschel and Dr. Ronald Zuker. The donor nerve is separated into fasciles before being attached to the cornea. (Hospital for Sick Children)

Corneal anesthesia happens when the nerve feeding the eye doesn't send pain signals back to the brain. Without that pain response, patients don't realize that tiny specks of dust and debris are getting into their eyes and scratching their corneas.

Over time, this seemingly minor damage accumulates and leads to scarring, and eventually permanent blindness.

"Most of the vision loss is from scar, and scar doesn't repair," explains Ali.

A life-ruining problem

The solution to this life-ruining problem came to Borschel after reading reports of a similar surgery attempted in the U.S. Surgeons tried to fix the problem of corneal anesthesia by redirecting a patient's nerves into the affected eye.

The surgery was an invasive 10-hour procedure that required an incision from ear to ear across the top of the head. It had exciting preliminary results, but no one picked it up and its originator retired.

Borschel explains that the procedure they devised at Sick Kids is much easier.

Rather than direct nerves across the top of the head, they take a small piece of the sural nerve from the patient's leg. Then they make a small incision above the eye that is not affected, attach the nerve to the other nerves of the forehead, and tunnel it under to the skin to reach the affected eye.

Then the nerve is disassembled into tiny nerve bundles called fascicles that are meticulously attached to the edges of the cornea.

The surgery requires the close co-operation of plastic surgeons like Borschel and Zuker, and ophthalmologists like Ali.

"It's a nice example of what can be achieved with a small number of committed people," says Borschel. "It's kind of a love story between plastic surgery and ophthalmology. Between two plastic surgeons and Dr. Ali, we managed to figure out something that works. It's a nice definitive solution to this problem."

A rare but devastating condition

Although it appeared that only a small number of patients would benefit from this new technique, the team continued its work. Explaining that drive, Borschel says, "It's a rare condition, but when it does occur it's devastating."

Their perseverance paid off when the team's results were presented at the World Society for Reconstructive Microsurgery meeting in Mumbai last March. Borschel remembers that after the presentation some of the Indian surgeons said, "We have this problem here, and it's often caused by leprosy."

In Canada most cases of corneal anesthesia are either congenital or due to brain tumours. But in the developing world infections are a major cause.

Though diseases like leprosy, also known as Hansen's disease, are rarely seen in North America, they affect over 200,000 people world wide.

Herpes is another unlikely culprit. "Children can get recurrent herpes; each time they get an episode they can lose sensation [in the eye]," explains Dr. Ali.

"These patients are very difficult to treat, there is no treatment actually," says Dr. Federico Vargas, who came to Sick Kids from Bogota, Colombia for a plastic surgery fellowship. Vargas' interest was in cleft palates, but when he saw the procedure he immediately saw the applications.

Luck strikes again

Then luck struck a second time because his colleague Dr. Mariana Cabrera, an ophthalmologist who is also from Bogota, was simultaneously doing a fellowship at Toronto Western Hospital.

"I was just talking with her about this type of procedure that I was learning here and she said, 'Oh my God! That's great because we have lots of patients [with corneal anesthesia] due to herpes infection,' " Vargas recalls.

Since this surgical pair found themselves in the same city at the same time, they both learned the procedure in anticipation of their return to Colombia.

Vargas explains that the new surgery is generating much interest in Latin America. After presenting the technique at a Colombian medical meeting, Vargas was asked to present it at The Bolivarian, a medical conference bringing together doctors from several South American countries.

"It's serendipitous," Borschel says as he looks back at the unlikely way this whole story evolved.

He admits the team never thought for one second their procedure would reach into the developing world to potentially prevent blindness in thousands of people.

"It's really quite interesting how something relatively small like this took off in such a very short amount of time."

Christopher Labos is a cardiologist and epidemiologist at the McGill University Health Centre. He is currently a fellow in global journalism at the Munk School of Global Affairs at the University of Toronto.