Keratoconus management shifts from replacing to remodeling the cornea

Theo Seiler

Keratoconus treatment no longer means replacing the cornea but instead remodeling it, according to a leading expert in the field.

“The management of keratectasia has undergone a complete change in paradigm in recent years. While 10 year ago, penetrating keratoplasty was the only option, today the choice is much wider. We can stop the disease, we can strengthen the cornea, we can intervene in terms of bulging back. It’s the time for remodeling the cornea,” Theo Seiler, MD, PhD, said at the meeting of the European Society of Cataract and Refractive Surgeons in Paris.

When replacement is necessary, it is different from in the past, he said. With the advent of deep lamellar techniques, PK is no longer performed to manage keratectasia. Keratoconus is a disease of the anterior stroma, in which the Descemet’s membrane and the endothelium are not affected and can be preserved.

DALK

“When transplantation is needed, we perform deep anterior lamellar keratoplasty (DALK). The weak stroma is removed, but the patient’s own endothelium is left in place. With this technique, we minimize rejection, have a faster rehabilitation and avoid surgically induced astigmatism,” Dr. Seiler said.

However, although far less invasive than PK, DALK is a time-consuming operation, lasting 1 hour or more compared to the 35- to 40-minute performance time of PK. In most European health care systems, the extra time does not bring in extra money for the physician, he said.

DALK is also a fairly difficult procedure, still leading to a 20% conversion rate due to Descemet’s perforation, he said.

Intracorneal rings

The idea of managing keratoconus by using support elements such as intracorneal rings was a first step toward the concept of remodeling.

“You add some stiff elements to the weak cornea. That’s the fundamental idea. Usually they are implanted at 70% of corneal thickness and produce a flatter, more regular cornea. The procedure is simple and fast, particularly when the femtosecond laser is used to perform the tunnels,” Dr. Seiler said.

This procedure is minimally invasive, but it has a 10% complication rate.

In addition, reliable prospective studies are still lacking, he said.

Collagen cross-linking

The latest revolutionary keratoconus treatment was UV collagen cross-linking. By tightening the collagen fibers in the stroma, this method produces profound changes in corneal biomechanics, making the tissue stronger and stiffer.

“This is what we call remodeling the cornea. Cross-linking has demonstrated to halt disease progression and in a minority of cases, it makes the ectasia bulge back, with consequent improvement of vision,” Dr. Seiler said.

He discussed the case of a young man who, 4 years after UV collagen cross-linking treatment, has fully regained emmetropia, starting from a –2 D.

“This was spectacular, certainly not the normal case. In most of the patients, additional visual rehabilitation is needed,” he noted.

The procedure is simple and fast. The failure rate is 3% and the complication rate is 10%.

Corneal cross-linking was prepared and supported by studies regarding the biomechanics of the cornea. The presence of a biomechanically weaker cornea in keratoconus patients was demonstrated by in vitro experiments, and the Ocular Response Analyzer (Reichert) has provided new parameters to measure corneal hysteresis.

“We are progressing, but we are still waiting for a technique to measure biomechanical properties in vivo,” Dr. Seiler said. – by Michela Cimberle

• Theo Seiler, MD, PhD, can be reached at Augenklinik Nordtrakt II, Frauenklinikstrasse 24, CH-8091 Zurich, Switzerland; +44-1-2554900; email: theo.seiler@iroc.ch.
• Disclosure: No products or companies are mentioned that would require financial disclosure.