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Anders Ivarsen, Kristian Næser, Jesper Hjortdal; Lasik In Highly Astigmatic Myopic And Hypermetropic Eyes. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1486.
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© ARVO (1962-2015); The Authors (2016-present)
Keratorefractive surgical treatment of astigmatism is generally considered less precise than spherical treatments. The present study is a retrospective evaluation of the refractive outcome after LASIK for high astigmatism in myopic and hypermetropic eyes.
Forty-six eyes with myopic astigmatism and 52 eyes with hypermetropic astigmatism were retrospectically identified from patient records at our clinic. In myopic patients, the preoperative refraction averaged -3.16 ± 2.55 diopters (D) in sphere (-10.00 to 0.00 D) and -3.92 ± 0.82 D in cylinder (-6.00 to -2.75 D). In hypermetropic eyes, the cycloplegic refraction averaged 3.51 ± 2.27 D in sphere (0.00 to 8.75 D) and -4.42 ± 1.10 D in cylinder (-6.50 to -2.00 D). All patients were examined before and 3 months after surgery. LASIK was performed with a Visumax femtosecond laser and a Carl Zeiss-Meditec MEL-80 excimer laser. Preoperative and postoperative astigmatisms were converted to polar values and the achieved correction of sphere and cylinder as well as the induced torsion were determined.
Three months after surgery, the average refraction in myopic eyes was 0.48 ± 0.68 D in sphere and -0.97 ± 0.52 D in cylinder. Polar analysis showed an astigmatic undercorrection of 0.77 ± 0.62 D (p < 0.01) and an induced torsion of -0.18 ± 0.51 D (p = 0.02). A weak correlation was found between intended astigmatic correction and the amount of undercorrection (r2 = 0.18, p < 0.01), with an undercorrection of 20% of the attempted correction. In myopic eyes, spherical correction was -0.01 ± 0.63 D from the intended (p = 0.40).In hypermetropic eyes, the 3-months refraction averaged 0.79 ± 0.83 D in sphere and -1.38 ± 0.90 D in cylinder. Polar analysis showed astigmatism to be undercorrected with 1.17 ± 0.81 D (<0.01), whereas the observed torsion of -0.17 ± 0.69 D was insignificant (p = 0.08). No significant correlation was found between intended astigmatic correction and the amount of undercorrection. Spherical correction was -0.01 ± 0.71 D from the intended value (p = 0.47).
In highly astigmatic eyes, the spherical correction obtained with LASIK was very close to the intended value. However, astigmatism was undercorrected, primarily in hypermetropic eyes. Astigmatic LASIK did not induce significant torsion.
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