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AE Barroso, O Baca, R Velasco, M Betech-Hanono, M Fromow; Bitoric Laser In Situ Keratomileusis For Mixed Astigmatism . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2073.
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Purpose:To assess the results and to evaluate the efficacy, safety, stability and predictability of bitoric laser in situ keratomileusis for the correction of mixed astigmatism. Methods:Thirty four eyes of 18 patients were treated by bitoric LASIK to correct mixed astigmatism using the Chiron Technolas Keracor 217 Excimer Laser System® and the Bausch & Lomb Surgical Hansatome® microkeratome.. Outcome measures included uncorrected visual acuity, manifest refraction, best corrected visual acuity, refractive predictability, refractive stability of spherical and cylinder corrections and postoperative change in lines of best corrected visual acuity. Vector analysis was used to determine the mean value of induced astigmatism and the mean axis shift. Postoperative results were evaluated at 1 and 3 months. Results:Preoperatively, the mean sphere was +1.8 ±1.11 diopters (D), with a mean cylinder of - 4.63 ±1.20 D. The mean preoperative spherical equivalent was -0.40 ± 0.80 D. At the last visit uncorrected visual acuity was 20/25 or better in 80% of all eyes treated with a mean spherical equivalent of – 0.07 ± 0.19 D. Average residual sphere was – 0.01 ± 0.98 D at 1 month and + 0.32 ± 0.34 D at 3 months. The mean residual cylinder was – 0.80 ± 0.32 and – 0.79 ± 0.47 at 1 and 3 months respectively. Three months after bitoric LASIK 86 % of eyes had a mean spherical equivalent within ± 0.50 D of emmetropia and none lost 2 or more lines of best corrected visual acuity. Vector analysis demonstrated a mean surgically induced cylinder of – 3.32 x 13º showed a tendency for with the rule changes after surgery. The average axis shift was 13 degrees. A mean decrease in vectorial magnitude of the astigmatism of 82.9 % was achieved. Conclusion:Bitoric LASIK is a safe, predictable and effective procedure to correct mixed astigmatism. We had favorable results with an expected but limited regression of the spherical component and stability of the cylinder correction. There was no loss of best corrected visual acuity. . In this study there was a tendency for induced with-the-rule astigmatism with statistical significance.
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