FDA approval underscores LADARVision status

Alcon's LADARVision® 4000 system recently became the first such system to receive FDA approval for wavefront-guided customised refractive surgery. The LADARVision® 4000 system includes the LADARVision®4000 Excimer Laser System and the LADARWave™ CustomCornea® Wavefront System. The approval was the culmination of the work of the Custom Cornea Study Group initiated by Marguerite McDonald MD, current president of the American Society of Cataract and Refractive Surgery and Director of the Southern Vision Institute in New Orleans, Louisiana, USA. Dr. McDonald performed the first cases in early 1999. She chaired the Nice symposium.

Dr. McDonald's colleague, Stephen Brint MD, also of the Southern Vision Institute in New Orleans reviewed the clinical data that led to the recent FDA approval. He also updated the attendees on more recent results with a refined treatment algorithm which was developed based on the FDA study results.

The FDA based its approval on the results obtained with 139 myopic eyes in an ongoing multi-centre clinical trial of the LADARWave™ CustomCornea® system. Patients in the US and Canada received wavefront-guided ablations in one eye and conventional myopic laser ablation (based on manifest refraction) in the other. Some 99% of patients in the trial achieved 20/40 or better UCVA, with the majority, 80%, reaching 20/20 or better.

All participants in the protocol underwent wavefront measurements with the LADARWave™ system aberrometer. The system takes five separate sequential measurements, selects the three closest in agreement and then averages those three. That forms the basis for the planned treatment. Each treatment consists of a 6.5 mm ablation zone with a blend zone out to 1.5 mm.

The results in the initial treatment group were sufficient to meet the criteria set by the FDA for approval. Using that algorithm, there was a tendency to slight undercorrection (0.25D to 0.50D) of the spherical component. The study was designed from the start to allow for refinements of the algorithm. The algorithm has been refined repeatedly since the first group was treated. The latest analysis reveals that the refined algorithm produced further improvements in outcomes without the undercorrection seen with the first algorithm.

In the FDA trial, nearly half of the patients in the custom ablation group, 48%, achieved vision of 20/16 or better uncorrected. Patients since treated with the modified algorithm did even better, with 57% reaching 20/16 at three months postoperatively. The modified algorithm also produced higher proportions of eyes reaching 20/20 uncorrected vision.

The enhanced algorithm also improved the accuracy of correction. While 69% of the initial treatment group was within 0.5D of the intended correction, this increased to 88% following the adjustment. The number within 1.0D of the target correction improved from 94% to 99%.

The researchers are also following changes in contrast sensitivity measured under scotopic and mesopic conditions. Some 2% of custom-treated eyes gained 0.3 log units at two or more spatial frequencies in photopic conditions, the amount considered significant by the FDA. In mesopic conditions, 15% gained contrast sensitivity as opposed to only 5% losing any sensitivity.

Participants in the trial also underwent psychometric testing. In the initial treatment group presented to FDA, most patients reported they felt they were seeing about the same, with a trend suggesting more felt they were seeing significantly better compared with those who felt they were seeing worse.

"This was the group that we felt were undercorrected. We thought once we had taken care of the undercorrection problem we would see these numbers change and indeed they did. The psychometric survey results from the refined algorithm group were much closer to target, looking at important parameters of glare, halo and night driving. Some 14% felt that night driving was significantly better than it was preoperatively. 10% reported a reduction in halo perception. Now we are seeing what we had hoped to see, a definite increase in patient satisfaction with night-time quality of vision."

The postoperative six-month data presented to the FDA indicated that the level of total higher order aberrations doubled in the conventional group, compared to the custom treatment group. The level of spherical aberrations was also twice as high in the conventional treatment group, as were trefoil and coma. Patients who have since been treated with the adjusted algorithm have shown virtually no increase in spherical aberration from preoperative levels.

"We want to know if we are preventing the induction of higher order aberrations, or treating existing aberrations and making them better? Using the modified algorithm, we believe the data is telling us that we are both reducing pre-existing total higher order aberration and spherical aberrations, as well as preventing the induction of new ones."

In an indication of how the field might be evolving, Dr. Brint also noted that some eyes have gone on to have custom retreatment of their initial custom ablation. He said the results had so far been "extremely good".