Latest-generation femtosecond laser enables fast, precise LASIK flap creation

Wavefront-guided ablation with bevel-in flap edge and smooth stromal bed shows trend toward reduced enhancement rates.

Christopher L. Blanton

A new-generation femtosecond laser created flaps for wavefront-guided LASIK more safely, rapidly and effectively than its predecessor, according to a study.

Christopher L. Blanton, MD, and colleagues compared the IntraLase FS 60-kHz and the iFS 150-kHz femtosecond lasers (Abbott Medical Optics) in creating flaps for wavefront-guided LASIK with iris registration.

The iFS laser afforded faster flap creation, lower energy level, smoother stromal beds and lower complication rates than the previous model.

The newer device also revealed a trend toward better visual acuity and lower enhancement rates than the older model, Dr. Blanton told Ocular Surgery News.

“The fact that the 150-kHz is faster is a big advantage,” he said. “First of all, because it takes you less time to make the flap, there’s less chance for a suction break, which can lead to complications. We are also able to demonstrate in a statistically significant way that you need less energy to make the flap. So, putting less energy into the eye once again shows promise for lowering complications.”

Dr. Blanton presented study results at the American Society of Cataract and Refractive Surgery meeting in Boston.

Patients and parameters

The retrospective study included 118 myopic eyes that underwent flap creation with the IntraLase FS with a 70° bevel-out side cut and 9/9 spot line separation. Fifty-one eyes underwent flap creation with the iFS with a 120° bevel-in side cut and 7/7 spot line separation.

Wavefront-guided ablation was performed in all cases with the Star S4 IR excimer laser with iris registration (AMO).

The primary requirement for inclusion in the study was no previous ocular surgery.

Eyes in the IntraLase FS laser group had a mean preoperative myopic spherical equivalent of –3.38 D (range: –0.625 D to –8.125 D). Eyes in the iFS group had a mean preoperative myopic spherical equivalent of –3.47 D (range: –1 D to –9.75 D). The difference between groups was statistically insignificant.

Investigators evaluated visual acuity at 1 day, 1 week, 1 month and 3 months postoperatively.

New benchmark for visual acuity

“Both platforms give excellent acuity results, high percentages of 20/15,” Dr. Blanton said. “In fact, in the 150-kHz group, at 3 months, every eye examined was 20/15, better than 20/20, which we were very pleased to see.”

At 1 month, 78.8% of eyes in the IntraLase FS group and 78.4% of eyes in the iFS group had uncorrected visual acuity of 20/15. At 3 months, 83.7% of eyes in the IntraLase FS group and 100% of eyes in the iFS group had UCVA of 20/15.

“I’m a huge fan of wavefront-guided procedures,” Dr. Blanton said. “There are multiple studies out now demonstrating that when you use a femtosecond flap creation with a wavefront-guided procedure, high percentages are better than 20/20. … 20/15 has become the new 20/20. We’re capable of hitting that at a very high percentage rate.”

However, between-group differences in UCVA were statistically insignificant; future study with more patients in the iFS group should result in more statistically valid data, he said.

Decreased spot line separation

Results showed that 4.2% of eyes in the IntraLase FS group and no eyes in the iFS group required enhancement, Dr. Blanton and colleagues reported.

“I’m going to revisit it with a larger pool of patients, but so far the trend is awfully good,” Dr. Blanton said.

Ablation time was 18 seconds in the IntraLase FS group and 12 seconds in the iFS group. The bed energy level was 1.17 mJ in the IntraLase FS group and 1.1 mJ in the iFS group. The difference was statistically significant (P = .032).

Dr. Blanton said decreased spot line separation afforded a smoother stromal bed.

“We have seen a smoother bed with the faster laser,” he said. “This is primarily because you can make the laser pulses closer together. … You can decrease the spot line separation to give you a smoother bed.”

One patient in the IntraLase FS group experienced bilateral flap dislocations. There were no flap complications in the iFS group. Dr. Blanton attributed flap stability in the iFS group to the 120° bevel-in edge.

“We think the bevel-in edge is a huge advantage,” he said.

Dr. Blanton and colleagues plan to present new data at the American Academy of Ophthalmology meeting in Chicago in October. – by Matt Hasson

• Christopher L. Blanton, MD, can be reached at Inland Eye Institute, 3257 E. Guasti Road, Suite 210, Ontario, CA 91761; phone: 909-937-9230 or 800-570-5273; mobile: 408-210-5191; e-mail: blanton007@aol.com. Dr. Blanton is a paid consultant to Abbott Medical Optics.