Femtosecond laser flap parameters and visual outcomes in laser in situ keratomileusis

To evaluate the flap-producing characteristics of the VisuMax femtosecond laser system and their relationship to visual and refractive outcomes after laser in situ keratomileusis (LASIK).

Dr. Sulaiman Al Habib Medical Center, Dubai Healthcare City, Dubai, United Arab Emirates.

Case series.

A review of LASIK cases from December 2008 to December 2009 was performed. Parameters recorded included the achieved flap thickness measured with intraoperative ultrasonic pachymetry, laser energy, side-cut angle, visual outcomes including uncorrected (UDVA) and corrected (CDVA) distance visual acuities and manifest refraction, higher-order aberrations using Hartman-Shack wavefront analysis, and complications.

The study comprised 98 patients (195 eyes). The femtosecond laser energy for flap preparation was 160 to 200 nJ. The mean achieved flap thickness was 91.35 μm ± 12.26 (SD) (attempted 80 μm), 98.5 ± 14.39 μm (attempted 90 μm), 109.94 ± 13.43 μm (attempted 100 μm), 112.7 ± 7.45 μm (attempted 110 μm), and 123.82 ± 9.64 μm (attempted 120 μm). Postoperatively, 87% of eyes were within ± 0.25 diopter of the intended spherical equivalent, 75% had a UDVA of 20/16 (-0.1 logMAR) or better, and 42% gained 1 or more lines of visual acuity; no eye lost CDVA. No statistically significant relationships were found between energy, side-cut angle, achieved flap thickness, and refractive and visual outcomes. Complications were mild and did not affect final visual outcomes.

The femtosecond laser yielded precise flap dimensions with a narrow standard deviation and a high level of safety.

Neither author has a financial or proprietary interest in any material or method mentioned.