How 'super vision' will redefine goal of LASIK

Clinical trial results-showing functional outcomes with a topography-guided LASIK procedure far surpassed those achieved with previous approaches-have stimulated further study aiming to identify parameters enabling even more consistent delivery of “super vision,” said Daniel S. Durrie, MD.

“The findings from the clinical trial leading to FDA approval of the topography-guided LASIK procedure [Contoura, Alcon Laboratories] suggest that we have gotten closer to the level of super vision we talked about earlier in the history of laser vision correction,” said Dr. Durrie, founder, Durrie Vision, Overland Park, KS, and clinical professor of ophthalmology and director of Refractive Surgery Services, University of Kansas Medical Center, Kansas City.

“Moving forward, we hope to truly redefine the goal of LASIK,” Dr. Durrie said.

“Instead of thinking about getting patients to see 20/20 uncorrected vision and out of the inconvenience of glasses or contact lenses, perhaps in the future we will be talking about getting them all to see 20/10 uncorrected and better than they could before with correction,” he said.

Refractive data from the FDA clinical trial that investigated the topography-guided LASIK procedure for treatment of myopia and mixed astigmatism showed that in terms of accuracy, the procedure performed as good as or better than anything achieved in clinical trials of previous ablation techniques. At 12 months, mean cylinder was 0.2 D and 95% of eyes were corrected within 0.5 D of intended.

Corresponding with the treatment accuracy, UCVA was 20/20 or better in 93% of eyes and 20/12.5 or better in 34%.

The finding that was particularly interesting, however, was that the proportion of eyes with UCVA of 20/10 or better increased significantly between month 3 and month 12. In a cohort of 230 eyes with complete data from the baseline, month 3 and month 12 visits, UCVA was 20/10 or better in 16 eyes at 3 months and in 36 eyes at month 12.

Intrigued by this novel finding, Dr. Durrie and co-investigators undertook a retrospective analysis of the clinical trial data to see if they could identify clinical factors associated with attainment of this “off the chart” level of uncorrected vision. What they found was that significant improvement in BCVA seemed to explain the improvement in UCVA.

Preoperatively, BCVA was 20/10 or better in only 2 eyes. At 3 months, 21 eyes had BCVA of 20/10 or better, including the 16 eyes that had 20/10 or better UCVA. At 12 months, 40 eyes had BCVA of 20/10 or better, including the 36 with 20/10 or better UCVA.

“We used to report how many eyes lost BCVA after LASIK,” Dr. Durrie said. “In this trial we found an unprecedented proportion of eyes that gained BCVA, showing that the treatment improved overall vision.”

He offered some ideas that could explain why the topography-guided procedure seems to provide better UCVA and BCVA outcomes than wavefront-optimized or wavefront-guided techniques. One possibility is that the topography-guided LASIK uniquely corrects higher-order aberrations on the cornea.

Another difference that might account for the performance of the topography-guided ablation is that it is centered on the corneal apex rather than on the pupil and thereby may compensate for some loss of vision that can occur with spectacle or contact lens wear.

Refining topography-guided LASIK

Dr. Durrie and colleagues believe that tapping into the potential promise of the topography-guided LASIK procedure requires further study to optimize the protocol, recognizing existing variations in technique.

He announced that in order to establish a standard that can most predictably deliver super vision, a physician-initiated study was organized that will analyze pooled data from 11 investigators having substantial experience with topography-guided LASIK to find factors associated with 20/10 or better UCVA.

Different surgeons describing different protocols for topography-guided LASIK are claiming theirs is the best, and that is creating some confusion.

“The aim of this study is to define the recipe for the ‘secret sauce’ that might allow us to get beyond the outcomes achieved in the clinical trial to where we can provide all or nearly all patients with super vision,” he said.

Dr. Durrie is a consultant to Alcon Laboratories.