Topography-guided LASIK and small-incision lenticule extraction (SMILE) were compared for the treatment of myopia and myopic astigmatism in a randomized, contralateral eye study. Results were good with both procedures, but at 3 and 12 months, there were statistically significant differences for most outcomes favoring LASIK.
By Cheryl Guttman Krader; Reviewed by A. John Kanellopoulos, MD
Results of a randomized study comparing topography-guided LASIK and small-incision lenticule extraction (SMILE) for treatment of myopia and myopic astigmatism favored LASIK when data were analyzed from the 3-month visit.
Findings from ongoing follow-up show refractive outcomes of both procedures remained stable to 12 months, and that refractive and visual acuity outcomes remained superior for LASIK, said A. John Kanellopoulos, MD.
The study compared the two techniques in contralateral eyes of 22 patients, noted Dr. Kanellopoulos, medical director, LaserVision.gr Clinical and Research Eye Institute, Athens, Greece, and clinical professor of ophthalmology, New York University Medical School, New York.
Eligible eyes had between –3.0 and –10 D of refractive error, and the parameters evaluated included uncorrected distance visual acuity (UDVA), corrected distance visual acuity, refractive error, corneal keratometry, contrast sensitivity, and Objective Scatter Index.
The LASIK procedure was performed with an excimer laser (Wavelight Ex500) and a femtosecond laser (FS 200) (both Alcon Laboratories). SMILE was performed with a femtosecond laser (VisuMax, Carl Zeiss Meditec).
While the outcomes were better with topography-guided LASIK, they were surprisingly good with SMILE considering several factors that put the femtosecond laser procedure at a disadvantage, Dr. Kanellopoulos noted.
“Some of the SMILE cases were part of my learning curve. Furthermore, with current SMILE technology, there is no cyclorotation compensation, one cannot do a topography-guided customized treatment, and it is not possible to reliably center on the vertex,” Dr. Kanellopoulos said. “These differences in technology likely explain the better results with topography-guided LASIK.”
The topography-guided LASIK used in this study included topographic adjustment of the amount and axis of astigmatism treated even though the eyes have regular astigmatism. Dr. Kanellopoulos introduced the technique, which is known as tomography-modified refraction, in a paper published in 2016 [Kanellopoulos AJ. Clin Ophthalmol. 2016;10:2213–2221].
“There is often a discrepancy between the refractive cylinder and amount of axis and the topographic-suggested values,” Dr. Kanellopoulos said. “We believe this is due to the fact that if angle kappa is over 50 μm, the cornea will have a prismatic effect and patients may change their absolute clinical refraction by adding virtual astigmatism and/or accommodative astigmatism for compensation.”
At 12 months, 100% of LASIK-treated eyes achieved UDVA of 20/20 compared with 81% of eyes in the SMILE group. The difference between groups was statistically significant, and the disparity favoring LASIK was even greater at higher levels of UDVA (20/16 and 20/10).
Statistically significant differences favoring LASIK were also seen in analyses of percentage of eyes achieving residual manifest spherical equivalent between 0.00 and +0.50 D and residual manifest refraction cylinder <0.25 D.
“This is where the difference probably spurred from the remarkably better cylindrical correction with the topography-guided LASIK,” he said.
The analysis of attempted versus achieved correction showed greater predictability with topography-guided LASIK. Larger deviations in SMILE eyes with >6 D of attempted correction were an important factor for the difference.
The Objective Scatter Index was better for LASIK-treated eyes earlier during follow-up while the outcome for the two procedures was more similar at 1 year. He suggested the findings may be explained by differences between procedures in the pattern of epithelial remodeling.
He described the contrast sensitivity results as surprising because in both groups and at most spatial frequencies, the postoperative results were better than the preoperative performance.
“These outcomes are testament to where we are at currently with laser vision correction,” Dr. Kanellopoulos said.
A. John Kanellopoulos, MD
The findings from follow-up to 3 months were published in 2017 [Kanellopoulos AJ. J Refract Surg. 2017;33:306-312]. The 12-month data were presented at the 2017 meeting of the American Academy of Ophthalmology. Dr. Kanellopoulos is a consultant to Alcon Laboratories and Carl Zeiss Meditec.