New Procedure Shows Promise for People with Keratoconus
Article Summary
- Bascom Palmer Eye Institute ophthalmologists offer corneal allogenic intrastromal ring segment (CAIRS) for some patients with keratoconus.
- Keratoconus is a form of corneal ectasia (or distention) where the cornea thins, warps and bulges out from the front of the eye.
- Dr. Rahul Tonk and Dr. Ellen Koo have performed several CAIRS procedures and are encouraged by the results.
For patients with keratoconus, the shape of the corneas become altered. In severe cases, patients are no longer able to read or drive a car.
The experts at Bascom Palmer Eye Institute, part of UHealth – the University of Miami Health System, offer a new option for the right candidates: a corneal allogenic intrastromal ring segment (CAIRS) procedure.
Treatment Options for Keratoconus
Keratoconus is a form of corneal ectasia (or distention) where the cornea thins, warps and bulges out from the front of the eye. The condition tends to develop in people in their 20s, 30s and 40s. It becomes a real quality-of-life issue when people start having vision problems and can no longer study or work, said Rahul Tonk, M.D., M.B.A., medical director of the Bascom Palmer Eye Institute at The Lennar Foundation Medical Center in Coral Gables, Florida, and associate professor of clinical ophthalmology at the University of Miami Miller School of Medicine.
People with milder keratoconus often undergo cross linking, a procedure that does not cure but can keep the condition from getting worse. People with advanced keratoconus typically have one option, corneal transplant surgery. That leaves a lot of people in between, and the options for correcting moderate keratoconus are less straightforward. CAIRS is one option.
“Pioneered by Dr. Soosan Jacob, the CAIRS technique is an additive procedure that helps to change the shape of the cornea,” said Bascom Palmer’s Ellen Koo, M.D., an associate professor of clinical ophthalmology at the Miller School. “By adding more tissue to the periphery, you are effectively changing the way light rays are being bent by the cornea.”
The technique involves inserting a ring of tissue within the cornea to change the shape back to as normal as possible. Dr. Tonk performed his first case of corneal tissue addition for keratoplasty (CTAK), a subtype of CAIRS, in June 2024. The patient was a 27-year-old man with advanced keratoconus who did not want to undergo corneal transplant.
“I told him about this new CTAK procedure. I counseled him that it may not necessarily work because his keratoconus was so advanced,” Dr. Tonk said. “But he didn’t have much to lose by trying, as his alternative was a more invasive corneal transplant.”
Dr. Tonk and Dr. Koo have now performed several cases and more are scheduled.
“We’re very encouraged by the results,” Dr. Tonk added.
A Better Implant?
Corneal ring segment implantation is not new, but earlier procedures involved placing hard, acrylic rings into the eye. The implants did not always correct vision to the point where corneal surgeons or patients were satisfied, Dr. Tonk said, and inserting foreign material into the eye can increase the risk for complications.
CAIRS implants allogenic donor corneal rings supplied by an eye bank or non-profit vision organization. The tissue is first treated with gamma irradiation to remove donor cells and DNA, leaving only layers of collagen for implantation. The recipient’s immune system will not reject the implant as foreign.
The insert can be shaped either manually or with a femtosecond laser.
“CAIRS is highly customizable, so the corneal tissue that is implanted is customized to the patient’s unique topography,” Dr. Tonk said.
To the patient, this procedure is akin to a LASIK treatment. It takes about 20 minutes and is usually done under light sedation with a local anesthetic. Recovery is generally three to seven days.
There’s an ongoing trial looking at results, “but what we’re seeing typically is an improvement on the best corrected vision of two to three lines on the chart.” Dr. Tonk said, “with more advanced patients seeing even more improvement.”
“The surgery can drastically improve vision and quality of life for patients with keratoconus,” Dr. Koo said.
But the doctors make sure to counsel patients in advance so they have realistic expectations.
“Our goal is to improve the corneal shape to where glasses can work well, not necessarily to eliminate the need for glasses or contacts overall,” Dr. Tonk said. “CAIRS puts people who don’t have an option to improve their vision without transplant into a much better position.”
AI and CAIRS
CAIRS technology is still in development. Artificial intelligence and machine learning could expedite advances in patient selection and outcomes. Currently, doctors may look at five to 10 variables when designing an implant for CAIRS, like age, steepness of the keratoconus or the thinness of the cornea. An AI algorithm can look at thousands of variables.
“The dream is, as the data improves with more postoperative results, that we can further improve our implant customization, and therefore our visual outcomes,” Dr. Tonk said.
Working at Bascom Palmer makes adoption of innovative procedures like CAIRS possible, Dr. Tonk said. The collaboration between Bascom Palmer and innovative physicians and scientists worldwide, including eye banks and industry partners, benefits patients in South Florida and around the world.
“Part of our mission is education. We don’t want this procedure to stay in one place or just a few places in the country or the world,” Dr. Tonk said. “We want to go out and educate corneal specialists across the country on the best practices we’ve learned with CAIRS, so more patients with keratoconus get the care that they need.”
Tags: Bascom Palmer Eye Institute, Dr. Ellen Koo, Dr. Rahul Tonk, eye diseases