Ladarvision excimer laser: Author reply

Abstract

As stated in the article, the data collected in the study represent the first eyes treated with the LADAR Vision system for LASIK hyperopia, hyperopic astigmatism, and mixed astigmatism. No prior data were available to assess LASIK outcomes for these refractive errors.At the beginning of the LASIK study, a nomogram adjustment of +1.00 diopters (D) was added to the sphere based on an initial analysis of eyes treated in a prior study of PRK correction of hyperopia and astigmatism. This adjustment was the best approach, based on a smaller data sample with only a few mixed astigmatic eyes. Because this was a study in support of Food and Drug Administration approval, the nomogram was standardized throughout the study to obtain a sufficient number of eyes treated in the same manner to support safety and effectiveness.Once we obtained a larger LASIK sample size by collecting data in this study, we were better able to assess outcomes for each refractive error type. Upon analysis of the LASIK study data, we determined that a 50% addition to the sphere was more appropriate than adding 1.00 D. The adjustment was also consistent among analysis by refractive error type. For the mixed astigmatic eyes, there was a trend for overcorrection with a preoperative sphere of <2 D when treated with the 1.00-D addition. Therefore, to prevent overcorrection, a 50% adjustment to the sphere was automated in the LADARVision system before commercial release of hyperopia, hyperopic astigmatism, and mixed astigmatism treatment.No nomogram adjustment to the cylinder component was applied to eyes treated in this study. The limited photorefractive keratectomy data available at the beginning of the study did not indicate a nomogram adjustment for cylinder.As Lyle et al recommend, sphere and cylinder components should be assessed independently for each type of refractive error to develop nomograms for optimal treatment outcomes. To perform this assessment, a baseline data sample must be collected. This first study provided such a baseline for the safety and effectiveness of LASIK correction of hyperopia, hyperopic astigmatism, and mixed astigmatism with the LADARVision system. As stated in the article, the data collected in the study represent the first eyes treated with the LADAR Vision system for LASIK hyperopia, hyperopic astigmatism, and mixed astigmatism. No prior data were available to assess LASIK outcomes for these refractive errors. At the beginning of the LASIK study, a nomogram adjustment of +1.00 diopters (D) was added to the sphere based on an initial analysis of eyes treated in a prior study of PRK correction of hyperopia and astigmatism. This adjustment was the best approach, based on a smaller data sample with only a few mixed astigmatic eyes. Because this was a study in support of Food and Drug Administration approval, the nomogram was standardized throughout the study to obtain a sufficient number of eyes treated in the same manner to support safety and effectiveness. Once we obtained a larger LASIK sample size by collecting data in this study, we were better able to assess outcomes for each refractive error type. Upon analysis of the LASIK study data, we determined that a 50% addition to the sphere was more appropriate than adding 1.00 D. The adjustment was also consistent among analysis by refractive error type. For the mixed astigmatic eyes, there was a trend for overcorrection with a preoperative sphere of <2 D when treated with the 1.00-D addition. Therefore, to prevent overcorrection, a 50% adjustment to the sphere was automated in the LADARVision system before commercial release of hyperopia, hyperopic astigmatism, and mixed astigmatism treatment. No nomogram adjustment to the cylinder component was applied to eyes treated in this study. The limited photorefractive keratectomy data available at the beginning of the study did not indicate a nomogram adjustment for cylinder. As Lyle et al recommend, sphere and cylinder components should be assessed independently for each type of refractive error to develop nomograms for optimal treatment outcomes. To perform this assessment, a baseline data sample must be collected. This first study provided such a baseline for the safety and effectiveness of LASIK correction of hyperopia, hyperopic astigmatism, and mixed astigmatism with the LADARVision system.