Improvement of keratorefractive lenticule creation by application of a vortex beam in a UV femtosecond laser system.

PURPOSE: To examine the effect of a vortex beam on gas formation and interface quality after keratorefractive lenticule creation with a 347 nm UV femtosecond laser.

SETTING

Anatomy Unit, University of Fribourg, Switzerland; Institute of Functional and Clinical Anatomy, University of Erlangen-Nürnberg, Erlangen, Germany; WaveLight GmbH, Erlangen, Germany.

DESIGN

Experimental study.

METHODS

Refractive corneal lenticules were created in 40 ex vivo porcine eyes with a 347 nm UV femtosecond laser. In 20 eyes, the laser was operated with a (Laguerre-Gaussian) vortex beam (generated by a spiral phase plate), and in the remaining 20 with a normal (Gaussian) beam. In each group, 12 eyes were used for histological quantification of intraoperative gas formation. The remaining 8 eyes were subjected to scanning electron microscopy after lenticule extraction to evaluate the lenticule bed morphology. The vortex group was compared morphologically and morphometrically with the normal group.

RESULTS

Application of a vortex beam significantly decreased the amount of gas produced intraoperatively. Semiquantitative 2D histomorphometrical analysis of the area occupied by gas bubbles yielded 20 156 ± 5591 μm 2 /mm in the normal samples, as compared with 9495 ± 3966 μm 2 /mm in the vortex samples ( P < .001). Moreover, the lenticule beds created by a UV vortex beam were markedly smoother and more regular than those created by a normal UV laser beam.

CONCLUSIONS

Operating a UV femtosecond laser with a vortex beam may significantly decrease the risk of opaque bubble layer formation and increases surgical safety and precision.