Algorithm provides superior results

July 1, 2012
Cheryl Guttman Krader, BS, Pharm

Data from 6 months of follow-up in a randomized, contralateral eye comparison study demonstrate LASIK performed using a proprietary "optimized prolate ablation" algorithm provides superior results compared with a conventional ablation technique.

Key Points

Chicago-Data from 6 months of follow-up in a randomized, contralateral eye comparison study demonstrate LASIK performed using a proprietary "optimized prolate ablation" algorithm (OPA, Nidek) provides superior results compared with a conventional ablation technique, said George O. Waring III, MD, at the annual meeting of the American Society of Cataract and Refractive Surgery.

Surgery was done by Alaa El-Danasoury, MD, at the Magrabi Eye Hospital in Jeddah, Saudi Arabia. Jack Holladay, MD, Houston, was a co-investigator. All treatments were performed using an excimer laser (EC-5000 CX III, Nidek) and a fourth-generation femtosecond laser (Intra-Lase, Abbott Medical Optics) to create LASIKflaps with an intended thickness of 110 μm.

"All laser refractive surgeons are aware of the issue of fall-off of radial pulse energy delivered to the peripheral cornea due to the oblique beam incidence," said Dr. Waring, emeritus professor of ophthalmology, Emory University, Atlanta, and private practice at Eye1st Vision and Laser, Atlanta.

"As a result, the prolate cornea is converted to an oblate shape in a standard myopic ablation, and there is induction of spherical aberration that compromises visual quality," Dr. Waring explained. "The OPA approach incorporates an eye-specific compensation matrix to adjust energy delivery in the periphery and also integrates topography in the ablation profile.

"It, thereby, targets an optimal corneal shape for a given eye, and the results of this study demonstrate the benefit of OPA for delivering better vision," he added.

Patients in the study were adults with –1 to –8 D of myopia, refractive cylinder <1.5 D, and an estimated residual stromal thickness exceeding 300 μm. The ablations were performed with the first version of the OPA software and the surgeon's personalized nomogram based on previous experience. All eyes were targeted for emmetropia, and with the OPA treatment, spherical aberration RMS was targeted for 0 μm.

All ablations were performed using iris recognition, online torsion correction, centration close to the visual axis instead of based on the entrance pupil, a large optical zone so that the entire pupil received the full treatment, and a blend zone.

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