Purpose: Evaluating the application of 2 methods for minimizing the ablated tissue upon objective minimization of depth and time of Zernike-based customized ablations.
Setting: Muscat Eye Laser Center, Muscat, Sultanate of Oman.
Methods: Recently developed algorithms for selection of Zernike terms in customized treatments for refractive surgery were used. Clinical outcomes and tissue-saving attributes were evaluated on 2 groups [minimize depth (MD) and minimize volume (MV); 30 eyes each], plus a control group [corneal wavefront (CW); 30 eyes] with conventional customized approach. Clinical outcomes were evaluated in terms of predictability, safety, and contrast sensitivity and tissue-saving attributes in terms of saved depth and time for each condition (in micrometers, seconds, and percentage) and whether minimized depth or time were less than required for equivalent noncustomized treatments.
Results: Ninety-three percent of treatments in the CW group, 93% in the MD group, and 100% in the MV group were within 0.50 diopters of spherical equivalent (SEq) postoperatively. Forty percent of treatments in the CW group, 34% in the MD group, and 47% in the MV group gained at least 1 line of best spectacle-corrected visual acuity postoperatively. Tissue-saving attributes showed an average saved depth of 8 μm (1-20 μm) and a saved time of 6 seconds (1-15 seconds) in the MD group and 6 μm (0-20 μm) and 8 seconds (2-26 seconds) in the MV group. Proposed corrections were always less deep and shorter than full wavefront corrections. In 43% of the MD cases, corrections were less deep, and in 40% of the MV cases, corrections were shorter than equivalent aberration-free treatments.
Conclusion: The minimization techniques compared here effectively reduced depth and time needed for ablation (up to a maximum of 50% and by 15% in average) without negatively affecting clinical outcomes postoperatively, yielding results equivalent to those of the full customization group.
From the *Instituto de Oftalmobiología Aplicada, University of Valladolid, Valladolid, Spain; †SCHWIND eye-tech-solutions, Kleinostheim, Germany; and ‡Muscat Eye Laser Center, Muscat, Sultanate of Oman.
Received for publication July 8, 2009; revision received December 17, 2009; accepted December 21, 2009.
M. C. Arbelaez has no proprietary interest in the materials presented herein.
S. Arba-Mosquera is an employee of SCHWIND eye-tech-solutions.
This article is part of the project of doctoral thesis by S. Arba-Mosquera at the research group “Refractive Surgery and Quality of Vision” at the Instituto Universitario de Oftalmobiología Aplicada, University of Valladolid, Spain.
Reprints: Samuel Arba-Mosquera, SCHWIND eye-tech-solutions, Kleinostheim, Germany (e-mail: firstname.lastname@example.org).