Anatomic outcomes of penetrating keratoplasty (PKP) have improved thanks to a number of innovations, but functional outcomes have still been suboptimal. The development of techniques based on use of the femtosecond laser to create host and donor incisions has driven PKP into a new era of refractive surgery.
"Lessons learned from refractive surgery have reshaped cataract surgery and are now reshaping corneal transplant surgery, driving it forward and adding excitement to a field that was lethargic for a long time," said Dr. Steinert, professor and chairman, Department of Ophthalmology, University of California (UC), Irvine. "With recent innovations, the emphasis for corneal transplant surgeons has shifted to providing good optical performance, rather than just achieving anatomical replacement."
He spoke during a symposium on the 25th anniversary of the excimer laser and drew a parallel between the advances occurring with that technology and research in corneal transplantation.
"Traditional corneal transplantation surgery has involved full-thickness PKP, and this procedure has had many triumphs in the past half century with the introduction of the operating microscope, development of better suturing material, introduction of corneal topography, . . . and increased understanding of the importance of controlling the ocular surface condition to improve graft survival," he said.
"However, a number of unsolved optical problems have remained," Dr. Steinert added. "Recovery of vision was painfully slow, and astigmatism limits functional rehabilitation."
Dr. Steinert and fellow colleagues at UC, including Marjan Farid, MD, are among various groups of researchers who have been working to develop new approaches to address the limitations of PKP, and their focus has been on femtosecond laser-enabled keratoplasty. The underlying goals for their project have been to minimize sources of astigmatism and aberrations by developing a technique that will enable improved graft alignment, reduced suture tension, and improved wound healing.
The work began in a laboratory using the then-available model of a proprietary femtosecond laser (IntraLase, Advanced Medical Optics) modified in a way that allows it to be focused deeper into the cornea. In their initial work using the laser to cut PKP incisions in a "top hat" shape, they demonstrated a dramatic improvement in resistance to wound leakage but without any real benefit in reducing astigmatism, Dr. Steinert said.
"We concluded that we had achieved proof of concept, and that justified moving ahead into clinical trials," he added.