WFO, WFG myopic PRK clinical outcomes compared

January 25, 2012

Results from a prospective randomized eye-to-eye study comparing wavefront-optimized (WFO) and wavefront-guided (WFG) myopic PRK show the WFO technique affords faster visual recovery, but ultimately, quantity and quality of vision appear to be better after WFG PRK, said co-investigators Anthony C. Liu, MD, and Edward Manche, MD.

Stanford, CA-Results from a prospective randomized eye-to-eye study comparing wavefront-optimized (WFO) and wavefront-guided (WFG) myopic PRK show the WFO technique affords faster visual recovery, but ultimately, quantity and quality of vision appear to be better after WFG PRK, said co-investigators Anthony C. Liu, MD, and Edward Manche, MD.

“By 3 months after surgery, both procedures were associated with excellent predictability and efficacy, and these results were maintained at follow-up through 12 months,” said Dr. Liu, resident, Department of Ophthalmology, Stanford University School of Medicine, Stanford, CA. “Safety was also excellent in both groups with no eyes developing significant corneal haze even though intraoperative mitomycin-C was not used.”

“However, our results also showed the WFO procedure induced more higher-order aberrations (HOAs) than WFG PRK, and eyes that underwent WFG PRK had better uncorrected visual acuity (UCVA) and 5% contrast acuity outcomes,” Dr. Liu added.

The study included 140 eyes of 70 subjects who underwent bilateral PRK with the eyes randomly assigned to treatment according to dominance. Dr. Manche, director, cornea and refractive surgery, and professor of ophthalmology, Stanford University School of Medicine, performed all of the surgeries. The WFG procedures were done using a proprietary excimer laser (VISX S4 CustomVue IR, Abbott Medical Optics) and WFO PRK was performed with a proprietary 400 Hz excimer laser (Allegretto Wave Eye-Q, Alcon Laboratories). Epithelial removal in all eyes was performed using an Amoils brush.

Patients had a mean age of 38 years and about two-thirds were women. As would be expected in a contralateral eye study, the two treatment groups were well matched in their baseline characteristics. In both groups, mean manifest SEQ was about –4.6 D and mean manifest cylinder was about +0.8 D. Mean total HOA RMS was 0.38 μm in the WFO eyes and 0.35 μm in the WFG group.

At 1 month after surgery, mean manifest SEQ was slightly myopic in both the WFG and WFO groups, –0.20 and –0.15 D, and both groups had a mean of just under +0.50 D of residual cylinder. At 12 months (37 patients), mean manifest SEQ was –0.15 D in the WFG eyes and –0.12 D in the WFO group, and mean cylinder was just under 0.25 D in both groups.

Predictability analyses showed that at all visits, >95% of eyes in both groups were within 1 D of their target refraction, and the results were equally excellent for the two procedures comparing them with a cut-off of ±0.5 D of target.

“The few outliers in each group represented eyes treated for higher levels of myopia,” Dr. Liu said.

Results from UCVA testing favored the WFO eyes over the WFG group in early follow-up through 1 month. At the first postoperative day, UCVA was 20/40 or better in 64% of WFO eyes and in 43% of WFG eyes; 17% of WFO eyes but only 7% of WFG eyes achieved UCVA of 20/20 or better. The proportion of eyes achieving UCVA of 20/20 or better increased to 30% for the WFO group at 1 week and was only 12% in the WFG group. While UCVA continued to improve in both groups, the results at 1 month still favored WFG treatment; UCVA was 20/16 or better in 56% of WFG eyes but in only 38% of WFO eyes.

At 3 and 6 months, UCVA was improved in both groups, and there was no difference between groups at those visits. At 12 months, however, there was a clear benefit for more eyes undergoing the WFG procedure to achieve higher levels of UCVA; 60% of WFG eyes compared with 46% of WFO eyes had UCVA of 20/12.5 or better at 12 months.

The wavefront analyses from follow-up at 3 months showed total HOA RMS and spherical aberration increased similarly in both groups whereas the WFO procedure induced more coma than the WFG treatment and the WFG group benefited with a greater reduction of trefoil. These results were stable at 6 and 12 months.

Data from follow-up at 6 and 12 months showed there were no eyes with a loss of more than 1 line of best spectacle corrected visual acuity (BSCVA).

Quality of vision was analyzed with testing of 5% and 25% contrast BSCVA. A gain of 1 or more lines of 5% contrast BSCVA was achieved by a majority of WFG eyes (51%), but by fewer eyes in the WFO group (39%). Improvements from baseline were less common among eyes that reached 12 months of follow-up, but still a higher proportion of eyes in the WFG group showed gains in 5% contrast BSCVA compared with the WFO group, 28% versus 19%. There was no difference between the groups at the 25% contrast acuity level.

Dr. Liu has no financial interest in the subject matter. Dr. Manche is an unpaid member of the medical advisory board for Abbott Medical Optics.

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