Spot diameters for scanning photorefractive keratectomy: a comparative study

Fabrice Manns; Jean-Marie A. Parel

doi:10.1117/12.309420

1 June 1998 Spot diameters for scanning photorefractive keratectomy: a comparative study

Fabrice Manns, Jean-Marie A. Parel

Proceedings Volume 3246, Ophthalmic Technologies VIII; (1998) https://doi.org/10.1117/12.309420
Event: BiOS '98 International Biomedical Optics Symposium, 1998, San Jose, CA, United States

Abstract

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 5 s 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.

Citation Download Citation

Fabrice Manns and Jean-Marie A. Parel "Spot diameters for scanning photorefractive keratectomy: a comparative study", Proc. SPIE 3246, Ophthalmic Technologies VIII, (1 June 1998); https://doi.org/10.1117/12.309420

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