17 May 1996 Evaluation of the smoothness and accuracy of scanning photorefractive keratectomy on PMMA by optical profilometry
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Abstract
The smoothness and accuracy of PMMA ablations with a prototype scanning photorefractive keratectomy (SPRK) system were evaluated by optical profilometry. A prototype frequency- quintupled Nd:YAG laser (Laser Harmonic, LaserSight, Orlando, FL) was used (wavelength: 213 nm, pulse duration: 15 ns, repetition rate: 10 Hz). The laser energy was delivered through two computer-controlled galvanometer scanners that were controlled with our own hardware and software. The system was programmed to create on a block of PMMA the ablations corresponding to the correction of 6 diopters of myopia with 60%, 70%, and 80% spot overlap. The energy was 1.25 mJ. After ablation, the topography of the samples was measured with an optical profilometer (UBM Messtechnik, Ettlingen, Germany). The ablation depth was 10 to 15 micrometer larger than expected. The surfaces created with 50% to 70% overlap exhibited large saw-tooth like variations, with a maximum peak to peak variation of approximately 20 micrometer. With 80% overlap, the rms roughness was 1.3 micrometer and the central flattening was 7 diopters. This study shows that scanning PRK can produce smooth and accurate ablations.
© (1996) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Fabrice Manns, Pascal O. Rol, Jean-Marie A. Parel, Armin Schmid, Jin-Hui Shen, Takaaki Matsui, Per G. Soederberg, "Evaluation of the smoothness and accuracy of scanning photorefractive keratectomy on PMMA by optical profilometry", Proc. SPIE 2673, Ophthalmic Technologies VI, (17 May 1996); doi: 10.1117/12.240048; https://doi.org/10.1117/12.240048
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