Smoothness and accuracy of PMMA ablations with a scanning photorefractive keratectomy system

F. Manns, P. Rol, J. M. Parel, A. Schmid, J. H. Shen, T. Matsui, P. Söderberg

Research output: Contribution to journalReview articlepeer-review


Purpose. To evaluate the smoothness and accuracy of PMMA ablations with a prototype scanning photorefractive keratectomy (SPRK) system. Methods. 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 beam was scanned with two galvanometer scanners 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 D of myopia with 60%, 70% and 80% spot overlap. The energy per pulse was 1.25 mJ and the spot diameter was 0.5 mm. The topography of the ablated samples was measured with an optical profilometer (UBM Messtechnik, Ettlingen, Germany). Results. The ablation depth was 10 to 15 μm 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 μm. With 80% overlap, the root mean square surface roughness was 1.3 μm and the central flattening was 7 D. Conclusions. SPRK can produce smooth and accurate ablations if the ablation per pulse is known precisely.

Original languageEnglish (US)
Pages (from-to)S574
JournalInvestigative Ophthalmology and Visual Science
Issue number3
StatePublished - Feb 15 1996

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems
  • Cellular and Molecular Neuroscience


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