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Proceedings Paper

Scanning photorefractive keratectomy at 213 nm: PMMA ablations
Author(s): Fabrice Manns; Pascal O. Rol; Martin Wosnitza; Patrick Maine; Jean-Marie A. Parel
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Paper Abstract

Purpose: In scanning photorefractive keratectomy, the corneal surface is reshaped by laser ablation with a scanning beam for the correction of myopia or astigmatism. A precise knowledge of the volume of corneal tissue removed by each laser pulse is necessary to be able to develop accurate ablation algorithms for scanning photorefractive keratectomy. The purpose of this study was to measure the ablation per pulse created on PMMA surfaces with a Q-switched frequency-quintupled Nd:YAG laser emitting at 213 nm. Methods: A frequency-quintupled Nd:YAG laser emitting at 213 nm with a pulse duration of 5 ns and a pulse energy of 1.2 to 1.5 mJ was used. The laser beam was focused on the surface of PMMA blocks and ablation craters were produced with 10, 50 and 100 pulses. The shape of the ablation craters was measured with an optical profilometer and compared with the beam profile measured with a laser beam diagnostic system. Results: The beam intensity distribution in the near-field consisted of two quasi-Gaussian peaks. The ablation craters contained two peaks. Assuming a Gaussian intensity distribution, the ablation per pulse in PMMA at 213 nm can be modeled by a parabolic function. Conclusions: Optical profilometry can be used to accurately measure the ablation per pulse and evaluate the homogeneity of the beam.

Paper Details

Date Published: 18 June 1999
PDF: 6 pages
Proc. SPIE 3591, Ophthalmic Technologies IX, (18 June 1999); doi: 10.1117/12.350577
Show Author Affiliations
Fabrice Manns, Univ. of Miami Bascom Palmer Eye Institute (United States)
Pascal O. Rol, Univ. of Miami and Univ. of Zurich (Switzerland)
Martin Wosnitza, Bascom Palmer Eye Clinic/Univ. of Miami School of Medicine (United States)
Patrick Maine, Big Sky Laser Technologies (United States)
Jean-Marie A. Parel, Univ. of Miami and Bascom Palmer Eye Institute (United States)

Published in SPIE Proceedings Vol. 3591:
Ophthalmic Technologies IX
Bruce E. Stuck; Pascal O. Rol; Michael Belkin; Karen Margaret Joos; Fabrice Manns; Bruce E. Stuck; Michael Belkin, Editor(s)

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