From VISION 2009 Volume 25, Number 1

A young patient with Hurler syndrome became one of the nation’s first successful cases of deep anterior lamellar keratoplasty (DALK) performed on a child by Duke ophthalmologist Terry Kim, MD.

The procedure is a benchmark in a new, layered approach to corneal transplants -- which could hasten the trend away from full-thickness corneal transplants for almost every patient with corneal disease.

Until recently, doctors performed full thickness transplants for any disease in the cornea, even if the disease affected only some of the corneal layers.

A now widely performed procedure known as Descemet’s stripping endothelial keratoplasty (DSEK) offers a more nuanced approach by replacing the back layer of the cornea. DALK takes it a step further -- it removes only the front 95 percent of the cornea, leaving the rest (including the Descemet’s membrane and endothelium) intact.

This new procedure presents significant advantages for pediatric patients, who face special challenges after corneal transplantation. In the case of Kim’s Hurler syndrome patient, the child’s genetic disorder was causing clouding in the cornea, requiring surgery to clear the clouded areas.

Since everyone’s endothelial cells degenerate over time, a donor cornea’s endothelial cells would not have lasted for this child’s lifetime. By leaving the Descemet’s membrane and endothelial cell layer intact, Kim says the DALK corneal transplant could last indefinitely.

Layered corneal transplant approaches such as DALK and DSEK could eventually replace full-thickness transplants altogether, according to Kim.

“We’re going through a revolution in corneal transplantation techniques and approaches,” he says. “DALK alone has the potential to replace 30 to 40 percent of the transplants we’re doing with conventional full-thickness transplant surgery.”

Both procedures offer faster recovery time, and they retain more structural integrity in the eye, since only the diseased portion of the cornea is replaced. DALK in particular offers a much lower risk of rejection because the body generally doesn’t sense the donor tissue in the outside layers of the cornea.

In addition, since there’s no need to penetrate into the eye, there’s less chance of complications such as bleeding, scarring, and glaucoma. And while DALK is still a delicate and difficult procedure, it’s not an all-or-nothing proposition.

“Right now surgeons can try these techniques, and if they don’t work out intraoperatively, they can convert over to a regular full-thickness transplant with relative ease,” says Kim.

Duke researchers and ophthalmologists are working in the laboratory to find ways to refine the technique by employing new imaging modalities such as SDOCT as well as other innovative devices that may help delineate the different layers of the cornea.

Together, surgical advances like DALK and DSEK, along with the new generations of adhesives, offer promise to patients suffering from a wide variety of eye diseases and conditions including corneal scarring, keratoconus, corneal ulcers, and corneal dystrophies.

“It’s been a really exciting time for corneal surgeons,” says Kim. “We are currently witnessing major advances in corneal transplantation surgery that should help ophthalmologists provide patients with better outcomes, faster recovery, and fewer complications.”