Bitoric laser in situ keratomileusis for the correction of simple myopic and mixed astigmatism

Objective: To evaluate the safety and efficacy of bitoric laser in situ keratomileusis (LASIK) for the correction of simple myopic and mixed astigmatism. Design: Retrospective, single-center, and noncomparative case series. Participants: Eighty-six eyes of 56 patients were analyzed for this study. Six-month and 1-year follow-up data were available on 86 eyes and 72 eyes, respectively. Eyes were divided in two groups according to the type of astigmatism: myopic astigmatism with low sphere (< -2 diopters) and mixed astigmatism. The range of astigmatism was 1.25 to 7.5 diopters, Intervention: LASIK was performed using the Automated Corneal Shaper (ACS) microkeratome (Bausch & Lomb, Claremont, CA) to create a cornea flap using the 130- or 160-micron thickness plate. A bitoric mid-stromal ablation was performed using the Nidek EC-5000 excimer laser (Nidek Company, Gamagori, Japan). Main Outcome Measures: Uncorrected visual acuity, manifest refraction, and best spectacle-corrected visual acuity were the parameters measured preoperatively and at months 1, 3, 6, and 12, Results: At the last visit, an uncorrected visual acuity of 20/20 or better was achieved in 77% and 68% of the myopic and mixed astigmatism groups, respectively. Ninety-two percent of all eyes had a mean spherical equivalent within +/- 0.50 diopter of emmetropia. A mean decrease in the vectorial magnitude of the astigmatism of 94% and 91% was achieved for those eyes with myopic and mixed astigmatism, respectively. There was no loss of best spectacle-corrected visual acuity, In two eyes, the axis of the positive cylinder was misaligned. Conclusion: Bitoric LASIK is an effective procedure to correct myopic and mixed astigmatism. Eighty-five percent of the eyes achieved an uncorrected visual acuity of 20/25 or better and had a final cylinder of 0.5 diopter or less. It is a safe operation, because no eyes lost any lines of best spectacle-corrected visual acuity. Longer follow-up may be needed to assess these results. Ophthalmology 2001;108:303-308 (C) 2001 by the American Academy of Ophthalmology.