Linda Roach

April 25, 2013

SAN FRANCISCO, California — A combination of 2 cutting-edge corneal procedures might give some patients with forme fruste keratoconus something to smile about.

The procedure pairs a femtosecond-laser assisted refractive surgery, called small-incision lenticule extraction (SMILE), with intrastromal corneal crosslinking.

Ophthalmologists from the Instituto de Oftalmología Conde de Valenciana in Mexico City say they have succeeded in stabilizing abnormal corneas for an average of 9 months and greatly improving patients' uncorrected visual acuity.

Ophthalmic surgeons have used corneal crosslinking with riboflavin and ultraviolet A for several years to stiffen the cornea's collagen matrix, which stops keratoconus and post-LASIK keratectasia. However, the refractive outcomes of these procedures have been disappointing, coauthor Gabriela Pagano, MD, told Medscape Medical News here at the American Society of Cataract and Refractive Surgery 2013 Symposium.

"The crosslinking is very good for halting progression, but refractively, it doesn't bring much to the patient," she said. With the combination, "we're bringing patients the possibility of spectacle independence."

The combined procedure has proven to be a safe, efficient, accurate, and predictable, with stable refractive outcomes, the researchers report.

Early results from this small case series look promising enough to a panel of keratorefractive discussants that they chose it as the Best Paper of the Session — setting off a flurry of congratulatory hugs for Dr. Pagano from other young corneal and refractive surgery fellows from Mexico, who were seated with her at the front of the room.

Best Paper

To treat the eyes, the researchers first incised a precisely shaped lenticule into the stroma with a femtosecond laser, then extracted the sliver of tissue through a short incision. The surgeons twice filled the pocket with riboflavin and irradiated the cornea with ultraviolet A, causing crosslinks to form within the stroma, Dr. Pagano explained.

The mean age of the 2 women and 2 men in this prospective, interventional case series was 31 years (range, 22 to 36 years).

All 4 participants had abnormal topography, corrected visual acuity of at least 20/40, 1 year of stable refraction, a spherical equivalent of −10 diopters or less with −5 diopters or less of astigmatism, and a preoperative corneal thickness greater than 400 μm.

Nine months after surgery, mean uncorrected visual acuity in the 7 study eyes had improved, from 20/400 at baseline to 20/25 after surgery (logMAR, 1.28 vs 0.11; < .001), Dr. Pagano reported.

Only 1 eye (14%) changed more than 0.5 diopters from month 1 to month 9.

Dr. Pagano pointed out that, if larger studies confirm the clinical value of this combined technique, the approach might have advantages over the commonly used solo crosslinking regimen, known as the Athens Protocol.

"It preserves Bowman's layer, which is considered one of the major factors of corneal strength. In theory, this should be better than other corneal refractive procedures," Dr. Pagano said. Because the corneal epithelium is not removed for the crosslinking treatment, pain is minimal and the risk for infection is lower, she said.

The combined technique is "very interesting, and probably a good solution for forme fruste keratoconus," said Michael Mrochen, PhD, professor of medical optics and physics at the Institute for Refractive and Ophthalmic Surgery at the Swiss Federal Institute of Technology in Zurich, who was asked by Medscape Medical News to comment on the study.

But Dr. Mrochen, who was part of the German–Swiss team that pioneered the corneal crosslinking "Dresden protocol," added that this study is too small and the follow-up too short (mean follow-up, 8.9 months) to determine efficacy.

However, "there seems to be a regression trend at the last follow-up. We know from crosslinking that data are stable after 12 months," he explained.

SMILE has limitations that could affect patients' refractive outcomes, he noted. "As can be seen from the data, the refractive predictability is not very good. However, SMILE procedures have difficulties with retreatment," Dr. Mrochen said.

Finally, there is the issue of optical higher-order aberrations that are characteristic of misshapen keratoconic corneas, he explained. "Forme fruste keratoconus typically has coma-like aberrations. SMILE is, to the best of my knowledge, not able to correct them."

The researchers had no external funding for the study. Coauthor Alejandro Navas, MD, is a consultant to Carl Zeiss Meditec and a member of the speakers bureau for Zeiss and STAAR Surgical. Coauthor Arturo Ramirez-Miranda, MD, reports receiving travel funding from Zeiss. Dr. Mrochen is president and research director for IROC Innocross, a Swiss company that sells crosslinking products.

American Society of Cataract and Refractive Surgery (ASCRS) 2013 Symposium: Paper session 2-D. Presented April 21, 2013.