A procedure gaining acceptance in Europe, the presbyopia laser treatment may have applications here in the U.S.
IntraCor treats the corneal stroma with a femto laser Source: Technolas
There are several surgical treatment options for presbyopia, among them multifocal and accommodating IOLs, intracorneal inlays, multifocal laser ablations, conductive keratoplasty, and scleral implants, but none has emerged as the true leading technology. Each option has its pros and cons, but one method that has begun to receive considerable attention in Europe is the IntraCor (Technolas Perfect Vision, Munich, Germany), a technique that applies femtosecond laser pulses to the corneal stroma without the need to create a flap or any other corneal incisions, said Mike P. Holzer, M.D., associate professor and director, refractive surgery, University of Heidelberg, Heidelberg, Germany. Originally performed by Luis Antonio Ruiz, M.D., Bogotá, Colombia, in 2007, Dr. Holzer said he performs the procedure with the TPV femtosecond laser (Technolas Perfect Vision), and has more than 1 year follow-up from his initial study patients (treated from July-October, 2008). In Europe, the IntraCor was approved in April 2009, he said. "The ideal patient is a presbyope with a little hyperopia, maybe +0.25 D to +1.5 D," he said. "Our group was followed for up to 18 months, and starting at months 1–3, there was stability in visual outcomes. That's really important for this type of patient. We are very glad to see the stability hold for such a long time."
Overall he said patients will find a "significant increase in near visual acuity on day 1 post-op; that stabilizes between 1 week and 1 month. They tend to gain just a little more from 1–3 months, but then it's really stable vision."
Understanding the technique
The IntraCor technique is noninvasive, and the actual correction lasts about 20 seconds, Dr. Holzer said. The laser creates gas bubbles that form in the cornea, which results in blurring the patient's vision for a couple of hours, he said. Once the bubbles dissolve and the cornea clears, the distance vision returns and "patients notice an immediate improvement in their near vision," he said. "Distance [visual acuity] doesn't really change, we've seen a slight myopic shift of about –0.4 D." Because of the slight shift, Dr. Holzer recommends patients be slightly hyperopic at baseline. In his study, inclusion criteria was presbyopia with a minimum near add of +2 D at 40 cm, hyperopia between 0.5 and 1.25 D, cylinder not greater than 0.5 D, and no prior ocular surgery. Patients also had to correct to 20/25 and have a minimum 500 micron corneal thickness, he said. (He added pupil size was measured with the Procyon pupillometer (Procyon, London) and near reading tests via the Sloan ETDRS near charts (Precision Vision, La Salle, Ill.), corneal topographies via the Pentacam HR (Oculus, Wetzlar, Germany) and endothelial cell counts with the Tomey EM 1000 (Tomey, Erglangen, Germany).) "We've done several tests on endothelial cell count and have not seen any change over time," Dr. Holzer said. "We also have not seen any significant changes in pre- and post-op stray light numbers." Patients are likely to notice "prominent rings around light sources at the very beginning. It's not true halo; patients notice but they're not truly bothered," he said.
Among Dr. Holzer's pearls: "You need a healthy cornea, ones without any scars or keratoconus. The work up is nothing out of the ordinary—wavefront measures and typical refractive surgery work-ups. The procedure itself takes about 15-20 seconds," he said. "Inclusion and exclusion criteria is no different than for any other refractive procedure." He also suggest surgery be performed first on the non-dominant eye.
Differences among the procedures
Although his group implants "a lot" of multifocal IOLs, in Germany the overall implantation rate in cataract surgery is "quite small, in the one-digit percentage rate," he said. IntraCor, however, is "a totally new patient group. We typically wouldn't do IOL surgery if there was no refractive error for distance," Dr. Holzer said. If a patient presents, for example, at +5 D for distance, "then we would recommend refractive lens exchange."
The IntraCor differs from the conductive keratoplasty "because it's focused into the deeper cornea," Dr. Holzer said. With IntraCor, "you're "cutting" into the cornea, but there's no dissection of the upper cornea; it's more like relaxing the cornea. That, in turn, leads to changes in asphericity that help with reading and near vision tasks. The cornea is left a little steeper at the center, not in the periphery."
Conductive keratoplasty also alters the corneal structure, but without the precision available with a femtosecond laser, Dr. Holzer said. "It's mostly a thermal thing. The outcome is not as predictable as a femtosecond laser can be."
Editor's note: Dr. Holzer has no financial interests related to his comments.
Holzer: +49 6221-566999, email@example.com