Wavefront-Guided Ablation: Evidence for Efficacy Compared to Traditional Ablation

Abstract

In the article by Netto and associates, 1 Netto M.V. Dupps Jr, W. Wilson S.E. Wavefront-guided ablation evidence for efficacy compared to traditional ablation. Am J Ophthalmol. 2006; 141: 360-368 Abstract Full Text Full Text PDF PubMed Scopus (62) Google Scholar the authors report on wavefront-guided ablation and its efficacy over traditional ablation. I appreciate the systematic approach the authors used to revisit every aspect of wavefront-guided treatment. However, I would like to comment on their take on custom LASIK as compared with custom PRK. The authors quote the work of Oshika and associates, 2 Oshika T. Klyce S.D. Applegate R.A. Howland H.C. El Danasoury M.A. Comparison of corneal wavefront aberrations after photorefractive keratectomy and laser in situ keratomileusis. Am J Ophthalmol. 1999; 127: 1-7 Abstract Full Text Full Text PDF PubMed Scopus (378) Google Scholar noting that “there was a significantly greater total higher order aberrations over a 7 mm pupil after custom LASIK compared with custom PRK.” First, I like to point out that Oshika and associates studied the corneal higher order aberrations after traditional LASIK and PRK; none of the study patients had customized ablation. Second, Oshika and associates emphasized in their article the fact that the two groups of patients had different transition zones. The LASIK group had a smaller laser ablation transition zone (6.5 mm) compared with the PRK group (7.0 mm). This is a major confounding factor in the study, and it could explain the difference in higher order aberrations between LASIK and PRK noted at the 7.0 mm pupil diameter. A smaller transition zone was opted in the LASIK group to prevent ablating the stromal side of the flap hinge, because the microkeratome they used cut a flap between 7.2 mm and 8.0 mm in diameter. More importantly, only spherical aberration over the 7.0 mm zone was higher in the LASIK group while coma levels were similar in both groups. In addition, the higher order aberrations at a smaller pupil size (3 mm) were similar in both groups. Creating a LASIK flap does somehow increase the higher order aberrations, but the significance of this is still unclear. 3 Waheed S. Chalita M.R. Xu M. Krueger R.R. Flap-induced and laser-induced ocular aberrations in a two-step LASIK procedure. J Refract Surg. 2005; 21: 346-352 PubMed Google Scholar , 4 Potgieter F.J. Roberts C. Cox I.G. et al. Prediction of flap response. J Cataract Refract Surg. 2005; 31: 106-114 Abstract Full Text Full Text PDF PubMed Scopus (47) Google Scholar , 5 Porter J. MacRae S. Yoon G. Roberts C. Cox I.G. Williams D.R. Separate effects of the microkeratome incision and laser ablation on the eye’s wave aberration. Am J Ophthalmol. 2003; 136: 327-337 Abstract Full Text Full Text PDF PubMed Scopus (123) Google Scholar I agree with Netto and associates that further studies, prospective and randomized, comparing higher order aberrations and visual quality after custom LASIK and customized surface ablation are needed to reach a meaningful conclusion. ReplyAmerican Journal of OphthalmologyVol. 141Issue 6PreviewWe thank Dr Awwad for pointing out limitations with the paper by Oshika and associates1 that we cited in our review article. Although there are a number of papers in the literature documenting an increase in higher order aberrations after formation of a LASIK flap, this article did not study custom ablation differences between PRK and LASIK. Full-Text PDF