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Interim results from analyses of data collected in the ongoing LASIK in U.S. Naval Aviator Study show advances in excimer and femtosecond laser technology are contributing to better clinical results.
To date, the study has enrolled 204 aviators who all were treated with wavefront-guided or wavefront-optimized LASIK and femtosecond flap creation. Dr. Tanzer reported findings from a cohort of patients with myopia treated with excimer laser vision correction (VISX S4 CustomVue) with Fourier algorithm and iris registration (IR) (when able) and using either the 60-kHz (IntraLase FS60) or 150-kHz (iFS) femtosecond laser (all Abbott Medical Optics [AMO]).
The top-line results showed that use of the 150-kHz device, the latest generation of the manufacturer's femtosecond laser, enabled a 16% higher IR capture rate relative to the 60-kHz model. In addition, the combination of the faster femtosecond laser and ablation with IR yielded the best outcomes in terms of faster visual recovery, better uncorrected visual acuity (UCVA), and low-contrast acuity.
The study protocol includes no nomogram adjustments for the wavefront-guided treatments, but the wavefront system (WaveScan WaveFront, AMO) is matched to the manifest refraction. All femtosecond laser flaps are created with an intended thickness of 110 µm and superior hinge. The flaps are cut with a 140° side-cut angle using the 150-kHz device and with a 70° side-cut angle using the 60-kHz femtosecond laser.
The group that had flap creation with the 60-kHz femtosecond laser was treated from July 2008 to January 2009 and included 136 eyes with a mean MRSE of –2.75 D (range –0.43 to –8.62 D); 85 (62.5%) eyes had an IR-enabled excimer laser ablation. The 150-kHz femtosecond laser was used in 155 subsequently enrolled patients with myopia whose mean MRSE was –2.59 D (range –0.34 to –6.64 D); 112 eyes (72.3%) had an IR-enabled procedure.
"The 150-kHz femtosecond laser creates a smoother stromal bed and this undoubtedly contributes to the higher IR capture rate," Dr. Tanzer said.