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The eyes with lower SE errors benefited the most from wavefront-guided treatment to reduce higher-order aberrations.
Scottsdale, AZ-When using the Allegretto laser system (WaveLight Laser Technologie AG), optimized (standard) LASIK and wavefront-guided LASIK have similar refractive and visual outcomes. However, eyes with substantial preoperative higher-order aberrations fare better if treated with wavefront-guided LASIK, according to Guy M. Kezirian, MD, FACS, sponsor and administrator of the U.S. FDA trials of the WaveLight Allegretto laser.
"Wavefront-optimized LASIK is designed to treat spherocylinder errors without affecting higher-order aberrations, especially spherical aberrations," Dr. Kezirian explained. "Treatment is based on input of the patient's refractive error, which is measured by phoropter in the laser. Wavefront-guided LASIK, on the other hand, treats both spherocylinder and higher-order aberrations."
The prospective controlled study was conducted at five U.S. sites. Patients were randomly assigned to bilateral treatment with either wavefront-guided LASIK or a control group for wavefront-optimized LASIK. Both groups were comparable in terms of demographics, age, refraction, and wavefront aberrations.
Comparing basic outcomes
"Both cohorts did similarly in the basic outcomes of refraction, visual acuity, and best-corrected visual acuity (BCVA). There were no significant differences between the two cohorts in the lower-order targets. No advantage was found for wavefront-guided treatments regarding these basic outcomes," he reported.
No patient lost two or more lines of vision in either cohort, and almost two-thirds of the eyes in both groups gained one or more lines of vision. "This is very significant because it indicated that the optics of the eye were improved by the treatment. This is in contrast to other lasers that get better BCVA with wavefront-guided LASIK, because the regular treatments cause some BCVA loss," Dr. Kezirian said.
All wavefront analysis was done in 6-mm pupils. Considering the distribution of higher-order aberrations, most eyes had 0.3 μm or less of root mean square (RMS) overall before surgery.
"When we evaluated how the treatment affected the higher-order aberrations, the eyes with 0.3 μm or less of preoperative RMS, there was no difference between the two cohorts; there was a mean minute increase (<0.1 μm) in aberration in both groups," he stated. "In eyes with more than 0.3 μm in preoperative RMS, it was very clear that wavefront-guided treatment reduced the aberrations more than wavefront-optimized treatment did."
Both the wavefront-guided treatment and the wavefront-optimized treatment performed with the Allegretto laser reduced higher-order aberrations. "The wavefront-guided treatment remarkably reduced higher-order aberrations, compared with the optimized treatment, which caused a slight reduction," he commented.
In commenting on the current discussion about the lack of effectiveness of wavefront-optimized treatment, he said, "This study cleared showed that wavefront-optimized treatment does not increase aberrations. This was a very exciting finding for me because of the frequency with which we use wavefront-optimized treatments."
When looking at the ability to change higher-order aberrations versus the preoperative degree of SE, there was no relationship for wavefront-optimized treatment. The eyes with lower SE errors benefited the most from wavefront-guided treatment to reduce higher-order aberrations.
"This makes sense because proportionately the higher-order aberrations are minute compared with the magnitude of the sphere and cylinder errors," Dr. Kezirian explained. "With corrections of very large sphere and cylinder errors, not much difference in higher-order changes will be noticed. However, if the sphere and cylinder error is relatively small, the higher-order aberrations become more important and those eyes will benefit."