Spot diameters for scanning photo-refractive keratectomy: A comparative study

Research output: Contribution to journalConference articlepeer-review


Purpose: The purpose of this study was to compare with computer simulations the duration, smoothness and accuracy of scanning photo-refractive keratectomy with spot diameters ranging from 0.2 to 1 mm. Methods: We calculated the number of pulses per diopter of flattening for spot sizes varying from 0.2 to 1 mm. We also computed the corneal shape after the correction of 4 diopters of myopia and 4 diopters of astigmatism with a 6 mm ablation zone and a spot size of 0.4 mm with 600 mJ/cm2 peak radiant exposure and 0.8 mm with 300 mJ/cm2 peak radiant exposure. The accuracy and smoothness of the ablations were compared. Results: The repetition rate required to produce corrections of myopia with a 6 mm ablation zone in a duration of 5s per diopter is on the order of 1 kHz for spot sizes smaller than 0.5 mm, and of 100 Hz for spot sizes larger than 0.5 mm. The accuracy and smoothness after the correction of myopia and astigmatism with small and large spot sizes were not significantly different. Conclusions: This study seems to indicate that there is no theoretical advantage for using either smaller spots with higher radiant exposures or larger spots with lower radiant exposures. However, at fixed radiant exposure, treatments with smaller spots require a larger duration of surgery but provide a better accuracy for the correction of astigmatism.

Original languageEnglish (US)
Pages (from-to)89-96
Number of pages8
JournalProceedings of SPIE - The International Society for Optical Engineering
StatePublished - Dec 1 1998
EventProceedings of Ophthalmic Technologies VIII - San Jose, CA, United States
Duration: Jan 24 1998Jan 25 1998


  • Ablation
  • Cornea
  • Laser
  • Model
  • Photorefractive keratectomy
  • Refractive surgery
  • Scanning

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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