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Flapless femtosecond laser procedure demonstrates unmatched efficacy in highly myopic eyes
Refractive results surpass those of femto-LASIK because of the lesser impact on corneal biomechanics, surgeon says.
ABU DHABI — Small-incision lenticule extraction is a predictable, safe and effective procedure, with unmatched results in highly myopic eyes, according to a presenter here.
Carl Zeiss Meditec ReLEx smile (small-incision lenticule extraction) is performed with the VisuMax femtosecond laser. A refractive lenticule is created within the intact cornea and removed through a small incision.
“We can handle patients with truly high myopia with this technique,” Osama Ibrahim, MD, said at an industry symposium held in conjunction with the World Ophthalmology Congress meeting. “In our 534 treated eyes with 1 year of follow-up, the preoperative mean spherical equivalent was –6.6 D, but the range was from –1.25 D to –17 D. At 1 week, results were marvelous, better than we used to see with regular LASIK with this high myopic group. The mean postoperative refraction was less than –0.25 D, ranging between +1.75 D and –3 D.”
Results
Because the ReLEx system only allows myopic correction up to –14 D, undercorrection was expected and intentionally aimed at in several study participants. Overcorrection, on the other hand, occurred in the initial cases in which a planar lenticule, about 15 µm thick, was performed to help surgeons find the edge and to facilitate dissection. Now that 5 µm lenticules are created, no overcorrection has been reported.
“We were also able to address astigmatism effectively, reducing it from mean 6 D preop to less than 0.25 D postop,” Dr. Ibrahim said.
Results were stable at 1, 3 and 6 months. At 1 year, the refractive range was between +1 D and –3 D, with still less than 0.25 D of cylinder.
“Safety was our main concern, because we were dealing with a new technology and had no experience,” Dr. Ibrahim said. “Some cases at the beginning lost a few lines of best corrected visual acuity, but the good news was that they regained them over time. After 1 year, only 1% had lost BCVA lines, which is not bad if you think that it was a group of high myopes, where BCVA is not easily maintained. What’s even more important is that most of the cases retained BCVA, or even gained one or two lines.”
Subgroup analysis dividing high, moderate and low myopia showed a comparable safety profile in all groups.
Uncorrected vision of 20/20 or better was achieved in 80% of patients. Refractive predictability was excellent, with 88% of eyes within ±0.5 D at 3 months and 99% of the eyes within ±1 D at 1 year.
Challenges, future developments
There are a few challenges in the smile procedure, of which centration is the most important, according to Dr. Ibrahim.
“The LASIK flap is more forgiving. Here you cut a lenticule and centration becomes really crucial,” he said.
Suction may be lost a few times at the beginning of the learning curve but is easily reapplied after drying the surface of the eye.
Having the right instruments for the dissection is also crucial because finding the dissection plane and freeing, grabbing and removing the lenticule can be cumbersome maneuvers at the beginning.
Dr. Ibrahim said he advises surgeons to begin with the ReLEx FLEx (femtosecond lenticule extraction) procedure to get acquainted with dissecting different planes before moving on to ReLEx smile.
“Compared to femto-LASIK, [ReLEx smile] has less of an impact on corneal biomechanics, and this makes results more stable,” he said. “It also allows correction of higher refractive errors, and it takes the same time for low and high correction. It is excellent in addressing astigmatism too, and there is less induction of high-order aberrations, while quality of vision, including contrast sensitivity, is as good as in femto-LASIK.”
Future improvements include a method of correcting the residual error, which is currently done by PRK or by converting the procedure into a flap procedure and doing a re-cut.
“[The] second big challenge is how to customize the treatment. We are working at a topo-guided or wavefront-guided customization. Finally, we also need the ability to correct hyperopia,” Dr. Ibrahim said. – by Michela Cimberle
For more information:
Osama Ibrahim, MD, can be reached at Alexandria University, El-Guish Road, El-Shatby, Alexandria – 21526, Egypt; +20-3-4252812 or +20-3-4252834; email: ibrosama@gmail.com.
Disclosure: Dr. Ibrahim is a consultant for Carl Zeiss Meditec.