Laser in situ keratomileusis correction of mixed astigmatism by bitoric ablation

Abstract

Purpose To evaluate the effect of bitoric ablation (cross cylinder) in 1 eye and ordinary monotoric treatment in the contralateral eye of patients with mixed astigmatism. Setting Instituto Oftalmológico de Alicante and University of Miguel Hernández, Alicante, Spain. Methods A comparative consecutive study was initiated in 30 eyes of 15 patients with mixed astigmatism. In each patient, 1 eye was treated with bitoric ablation (Group 1) and the other eye was treated with monotoric ablation (Group 2). The decision to treat with bitoric or monotoric ablation was randomized. All patients were operated on by the same surgeon (J.L.A.) and examined by the same investigators (M.J.A., M.A.H.). All completed a 6-month follow-up. Visual acuity was estimated by transforming the Snellen chart readings into logMAR equivalents. In Group 1, theoretical ablation was also performed on glass slides by making 3 ablation profiles (positive, negative, and bitoric). Results There was a statistically significant improvement in the mean uncorrected visual acuity (UCVA), the mean spherical equivalent (SE), and the mean refractive cylinder in Group 1 ( P<.0001, P = .04, P<.0001, respectively) and in the mean refractive cylinder in Group 2 ( P = .01). Better results were obtained in the mean incremental change in UCVA, best corrected visual acuity, SE, and refractive cylinder in Group 1. Conclusions Treatments to correct mixed astigmatism vary in ablation profiles and depth. Bitoric ablation appears to be safer, more effective, and more tissue sparing than the standard treatment.