Lara C. Pullen, PhD

April 27, 2012

April 26, 2012 (Chicago, Illinois) — The variable spot-scanning (VSS) refractive software for myopic LASIK surgery provides surgeons with an acceptable alternative to conventional treatment. In addition, a new wavefront-guided system is being developed that will provide surgeons with an effective and safe alternative to conventional LASIK.

W. Bruce Jackson, MD, from the University of Ottawa Eye Institute in Ontario, Canada, presented 2 studies on LASIK surgery here at American Society of Cataract and Refractive Surgery 2012 Symposium on Cataract, IOL and Refractive Surgery. He sat down with Medscape Medical News to discuss his research.

His first presentation was a poster describing a prospective study designed to evaluate the performance and acceptability of VSS refractive ablations with an excimer laser system. VSS refractive treatment is an alternative to conventional treatment when a WaveScan wavefront measurement is not available.

Dr. Jackson explained that "the intention was to upgrade the conventional program and be able to offer this one when you couldn't do wavefront."

The VSS refractive software is different from conventional software because it allows for better cosine compensation and optical and ablation zone management. The beam size provides a more exacting fit to the Munnerlyn shape. In addition, the VSS refractive software uses VSS and variable repetition rate to temporally and thermally control ablations in the most efficient manner.

Conventional treatment is defined by the major axis of the optical zone. The minor axis of the optical zone is based on the amount of astigmatism, and can be as small as 4.5 mm.

In contrast, VSS refractive treatment is defined by the minimum optimal zone. Maximum optimal zone is determined based on the amount of astigmatism and is at least as big as the minimum optical zone.

The open-label nonrandomized clinical trial was performed at 5 centers in Canada. To date, 110 eyes have been enrolled in the myopic cohort. LASIK was performed with the Star S4 IR excimer laser system. All flaps were made with an IntraLase femtosecond laser. The treatments were based on manifest refraction with no nomogram adjustments. VSS spot size was 0.65 to 6.5 mm and variable repetition rate was 6 to 20 Hz. There was no iris registration.

VSS Refractive Treatment Safe and Effective

Manifest refraction spherical equivalent was achieved within 2.0 diopters for all eyes, and within 0.5 diopters for 74% of eyes.

All established criteria for safety and efficacy were met at the 3-month visit. VSS refractive treatment demonstrated good refractive stability over time. No eye lost 2 or more lines of uncorrected distance visual acuity (UDVA) at 1 month or beyond.

Overall, in the cohort analyzed, the results compared favorably with previous trials for laser vision correction using the STAR S4 IR excimer laser system.

Dr. Jackson explained that the VSS refractive procedure "really is a value, but it's going to be a value internationally.... It's not going to see the light of day in the United States."

Instead, he described the iDesign system that will proceed to clinical trials in the United States. Dr. Jackson anticipates that the iDesign will first be commercially available in Japan.

Medscape Medical News contacted Guillermo Rocha, MD, from the GRMC Vision Centre in Brandon, Manitoba, Canada, to get another perspective on the new technique. Dr. Brandon reported by email that he currently uses the VSS refractive procedure fairly routinely. He added that "iDesign looks very interesting in the sense that all preoperative data are incorporated into a single device. This should provide more consistency in planning the surgery, and less room for input errors."

iDesign Provides Excellent Visual Results

iDesign is an advanced wavefront-guided system that has also been studied by Dr. Jackson. He presented the results of a prospective, multicenter, open-label, nonrandomized, clinical trial that was completed at 4 sites in Canada. The study involved 108 myopic eyes.

At 6 months, 77% of eyes had 20/16 UDVA or better, and 93% had 20/20 UDVA or better. Dr. Jackson reported that 81% of eyes were within 0.5 diopters of their target manifest refraction spherical equivalent.

Dr. Jackson is extremely enthusiastic about the results. He described the technique, explaining that "out of the box, we made no adjustments." Even more important, however, he described the positive results in the patients: "They're the happiest patients that we've got.... When we saw them, they had smiles on their faces."

Results Are Impressive and Raise the Bar

Dr. Rocha agrees that the results are impressive. "Typically, we have measured refractive surgery results in patients achieving 20/25 or 20/20 vision. In this presentation, the bar is raised, with the authors reporting a significant percentage of patients achieving better than 20/20 vision (i.e., 20/16.0 and 20/12.5). In addition, the fact that over 80% of eyes achieve a result within 0.50 diopters of the intended target is quite significant."

Dr. Jackson reports receiving a research grant from Abbott Medical Optics. Dr. Rocha reports being a consultant for Abbott Medical Optics, but not as it pertains to laser surgery.

American Society of Cataract and Refractive Surgery (ASCRS) 2012 Symposium on Cataract, IOL and Refractive Surgery: Poster P202, presented April 20, 2012; iDesign presented April 26, 2012.