Femtosecond laser, keratome provide similar results

Palo Alto, CA-A prospective comparison study of the IntraLase femtosecond laser (IntraLase Corp.) and the Hansatome keratome (Bausch & Lomb) in myopic LASIK with VISX CustomVue (Advanced Medical Optics) showed that both devices produced excellent visual outcomes. The eyes treated with the femtosecond laser showed more improvement in several outcome measures at early intervals in the study, but most of these differences had disappeared by 6 months, said Edward E. Manche, MD.

The eyes treated with the femtosecond laser had significantly better uncorrected visual acuity (UCVA) at 1 week, 1 month, and 3 months, although the difference evaporated by 6 months. Eyes treated with the femtosecond laser experienced a statistically significant advantage in the change from baseline best-corrected visual acuity (BCVA) to postoperative UCVA through 6 months; however, a statistically significant improvement in BCVA from baseline to 3 months in favor of the femtosecond laser group disappeared by 6 months.

Dr. Manche, associate professor of ophthalmology, Stanford University Medical Center, Palo Alto, CA, speculated that a lower residual cylinder in the femtosecond laser group during the early postoperative period could have influenced the finding that some of the differences between the two treatment groups were no longer apparent at the 6-month evaluation.

In the study, myopic LASIK using the VISX CustomVue was performed on 100 eyes of 50 subjects. One eye was randomly assigned to treatment with the femtosecond laser and the other with the Hansatome keratome. Ocular dominance was not determined.

Nomogram analysis prior to study initiation indicated that best results would be achieved by using a slight offset to the Hansatome and no offset to the femto-second laser. Following installation of a Fourier software upgrade after the first eight subjects had been treated, no offsets were performed.

Patients ranged from 25 to 59 years of age with a mean age of 39.8 ± 7.8; 60% were female. Preoperatively, the groups were closely matched for manifest sphere, cylinder, and spherical refraction. Sphere was –3.96 ± 1.48 D in the femtosecond laser group and –3.95 ± 1.44 D in the keratome group. Total higher-order aberrations were 5.2 ± 2.0 for the femtosecond laser-treated patients and 5.1 ± 2.1 for the keratome group. There were no statistically significant differences between the groups.

Intraoperatively the femtosecond laser was programmed at a depth setting of 110 μm with a flap diameter of 9.2 mm; the mean flap thickness was 118.6 ± 18.7 μm. With the Hansatome, investigators used a 160-μm head with a 9.5-mm range and achieved a mean flap thickness of 137.0 ± 21.7 μm.

There were no significant complications in either group. One patient in the femtosecond laser group had a narrow hinge, and three patients had loose epithelium in both eyes.

Day 1 outcomes showed no statistically significant differences between the groups. Outcomes were excellent, Dr. Manche said, with more than 95% of patients in each group attaining 20/20 vision or better. At 1 month, a greater percentage of eyes in the femtosecond laser group achieved 20/12.5 or better, which was statistically significant (94% versus 74%, p = 0.05).

This finding held up at the 3-month follow-up (89% versus 70%, p = 0.06) but weakened over time.

"At 6 months, even though there is a slight trend to the femtosecond laser group, there was no statistically significant difference between the two groups [90% versus 86%, p = 0.13]," Dr. Manche said.

He also analyzed postoperative UCVA compared with preoperative best spectacle-corrected visual acuity. "At 1 month, the IntraLase group had a greater percentage of eyes gaining lines with uncorrected vision compared with their preoperative best-corrected vision," Dr. Manche said. "This held at 3 and 6 months, with 38% of the femtosecond laser-treated eyes gaining 1 or more lines of uncorrected visual acuity compared with 19% in the Hansatome group [p = 0.02]."