Single zone versus multizone photorefractive keratectomy: Theoretical comparison

X. Gonzalez-Cirre, Fabrice Manns, Jean-Marie A Parel

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Abstract

Purpose. To evaluate the theoretical advantages of multiple zone ablations for the correction of high myopia by photorefractive keratectomy (PRK). Methods. The point spread functions (PSF) of a modified paraxial eye model were computed with a pupil diameter of 2 to 8 mm after single, double, and triple zone PRK for the correction of 10D of myopia. The triple zone was divided as follows: 50% (5D) at 5 mm, 30% (3D) at 5.5 mm, 20% (2D) at 6 mm. The double zone was divided in two zones with diameters 5 and 6 mm. The amount of correction in each zone was calculated so that the central ablation depth was the same as for the triple zone. The diameter of the single zone was selected so that the central ablation depth was the same as for the triple zone. Results. Ablation depth: The central ablation depth with the triple zone is 96 μm. The central ablation depth is the same with the double zone when 70% of the initial myopia is corrected at 5 mm and 30% at 6 mm, and with a 5.5 mm single zone. PSF: The PSF consist of the PSF of the emmetropic eye and of a set of concentric annuli (halos) corresponding to each zone. With the triple and double zones, the first halo appears when the pupil diameter is larger than 4.2 mm. With the single zone, the halo appears when the pupil diameter is larger than 4.6 mm. Conclusions. Single zone ablations seem to be more advantageous in theory than multiple zone ablations for the correction of high myopia by PRK.

Original languageEnglish
JournalInvestigative Ophthalmology and Visual Science
Volume37
Issue number3
StatePublished - Feb 15 1996

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Photorefractive Keratectomy
Myopia
Pupil

ASJC Scopus subject areas

  • Ophthalmology

Cite this

@article{6c32c578091c4ecfaccf7e4b694c068e,
title = "Single zone versus multizone photorefractive keratectomy: Theoretical comparison",
abstract = "Purpose. To evaluate the theoretical advantages of multiple zone ablations for the correction of high myopia by photorefractive keratectomy (PRK). Methods. The point spread functions (PSF) of a modified paraxial eye model were computed with a pupil diameter of 2 to 8 mm after single, double, and triple zone PRK for the correction of 10D of myopia. The triple zone was divided as follows: 50{\%} (5D) at 5 mm, 30{\%} (3D) at 5.5 mm, 20{\%} (2D) at 6 mm. The double zone was divided in two zones with diameters 5 and 6 mm. The amount of correction in each zone was calculated so that the central ablation depth was the same as for the triple zone. The diameter of the single zone was selected so that the central ablation depth was the same as for the triple zone. Results. Ablation depth: The central ablation depth with the triple zone is 96 μm. The central ablation depth is the same with the double zone when 70{\%} of the initial myopia is corrected at 5 mm and 30{\%} at 6 mm, and with a 5.5 mm single zone. PSF: The PSF consist of the PSF of the emmetropic eye and of a set of concentric annuli (halos) corresponding to each zone. With the triple and double zones, the first halo appears when the pupil diameter is larger than 4.2 mm. With the single zone, the halo appears when the pupil diameter is larger than 4.6 mm. Conclusions. Single zone ablations seem to be more advantageous in theory than multiple zone ablations for the correction of high myopia by PRK.",
author = "X. Gonzalez-Cirre and Fabrice Manns and Parel, {Jean-Marie A}",
year = "1996",
month = "2",
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language = "English",
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journal = "Investigative Ophthalmology and Visual Science",
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AU - Manns, Fabrice

AU - Parel, Jean-Marie A

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Y1 - 1996/2/15

N2 - Purpose. To evaluate the theoretical advantages of multiple zone ablations for the correction of high myopia by photorefractive keratectomy (PRK). Methods. The point spread functions (PSF) of a modified paraxial eye model were computed with a pupil diameter of 2 to 8 mm after single, double, and triple zone PRK for the correction of 10D of myopia. The triple zone was divided as follows: 50% (5D) at 5 mm, 30% (3D) at 5.5 mm, 20% (2D) at 6 mm. The double zone was divided in two zones with diameters 5 and 6 mm. The amount of correction in each zone was calculated so that the central ablation depth was the same as for the triple zone. The diameter of the single zone was selected so that the central ablation depth was the same as for the triple zone. Results. Ablation depth: The central ablation depth with the triple zone is 96 μm. The central ablation depth is the same with the double zone when 70% of the initial myopia is corrected at 5 mm and 30% at 6 mm, and with a 5.5 mm single zone. PSF: The PSF consist of the PSF of the emmetropic eye and of a set of concentric annuli (halos) corresponding to each zone. With the triple and double zones, the first halo appears when the pupil diameter is larger than 4.2 mm. With the single zone, the halo appears when the pupil diameter is larger than 4.6 mm. Conclusions. Single zone ablations seem to be more advantageous in theory than multiple zone ablations for the correction of high myopia by PRK.

AB - Purpose. To evaluate the theoretical advantages of multiple zone ablations for the correction of high myopia by photorefractive keratectomy (PRK). Methods. The point spread functions (PSF) of a modified paraxial eye model were computed with a pupil diameter of 2 to 8 mm after single, double, and triple zone PRK for the correction of 10D of myopia. The triple zone was divided as follows: 50% (5D) at 5 mm, 30% (3D) at 5.5 mm, 20% (2D) at 6 mm. The double zone was divided in two zones with diameters 5 and 6 mm. The amount of correction in each zone was calculated so that the central ablation depth was the same as for the triple zone. The diameter of the single zone was selected so that the central ablation depth was the same as for the triple zone. Results. Ablation depth: The central ablation depth with the triple zone is 96 μm. The central ablation depth is the same with the double zone when 70% of the initial myopia is corrected at 5 mm and 30% at 6 mm, and with a 5.5 mm single zone. PSF: The PSF consist of the PSF of the emmetropic eye and of a set of concentric annuli (halos) corresponding to each zone. With the triple and double zones, the first halo appears when the pupil diameter is larger than 4.2 mm. With the single zone, the halo appears when the pupil diameter is larger than 4.6 mm. Conclusions. Single zone ablations seem to be more advantageous in theory than multiple zone ablations for the correction of high myopia by PRK.

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