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

Abstract

Purpose: 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).

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

Design: Case series.

Methods: 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.

Results: 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.

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

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