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Letter

Correction factor for ablation algorithms considering decentration and transition zones

Jimenez, José Ramón PhD; Anera, Rosario González PhD

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Journal of Cataract & Refractive Surgery: May 2014 - Volume 40 - Issue 5 - p 850
doi: 10.1016/j.jcrs.2014.02.023
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Fang et al.1 analyzed aberrations caused by decentration treatment and optical zones after myopic corneal surgery. The analysis of experimental data presented in the article is based on the use of adjustment factors for ablation algorithms used for different conditions. These adjustment factors consider oblique incidence, reflection losses, and nonlinear incidence on the cornea and other factors that influence corneal ablation.

The methodology used to deduce these factors was published by Jiménez et al.2 and used in subsequent papers.3,4 In addition, adjustment factor K, used in method 2 and published in Fang et al.’s paper, is

with cosα accounting for nonnormal incidence and [1-R] for reflection losses.

This adjustment factor is exactly the same adjustment factor deduced and used by Jiménez et al.2 to consider reflection losses in the cornea and non-normal incidence. The factor deduced by Jiménez et al. has been jointly considered with other aspects, such as the type of algorithm,3 the Gaussian shape of the beam,4 and oblique incidence,5 among others. As other authors have shown,1–5 the methodology of proposing adjustment factors for correcting ablation algorithms is very useful and can be used to diminish the differences between postsurgical expected and real corneal shape; these corneal differences reduce the postsurgical visual performance and quality in patients.

References

1. Fang L, Wang Y, He X. Theoretical analysis of wavefront aberration caused by treatment decentration and transition zone after custom myopic laser refractive surgery. J Cataract Refract Surg. 2013;39:1336-1347.
2. Jiménez JR, Anera RG, Jiménez del Barco L, Hita E. Effect on laser-ablation algorithms of reflection losses and nonnormal incidence on the anterior cornea. Appl Phys Lett. 81, 2002, p. 1521-1523, Available at: http://hera.ugr.es/doi/15014654.pdf. Accessed February 8, 2014.
3. Jimenez JR, Anera RG, Díaz JA, Pérez-Ocón F. Corneal asphericity after refractive surgery when the Munnerlyn formula is applied. J Opt Soc Am A Opt Image Sci Vis. 2004;21:98-103.
4. Jiménez JR, Anera RG, Jiménez del Barco L, Hita E, Pérez-Ocón F. Correction factor for ablation algorithms used in corneal refractive surgery with gaussian-profile beams. Opt Express. 13, 2005, p. 336-343, Available at: http://www.opticsinfobase.org/oe/viewmedia.cfm?uri=oe-13-1-336&seq=0. Accessed February 8, 2014.
5. Fang L, Wang Y, He X. Effect of pupil size on residual wavefront aberration with transition zone after customized laser refractive surgery. Opt Express. 21, 2013, p. 1404-1416, Available at: http://www.opticsinfobase.org/oe/viewmedia.cfm?uri=oe-21-2-1404&seq=0. Accessed February 8, 2014.
© 2014 by Lippincott Williams & Wilkins, Inc.