Comparison of laser in situ keratomileusis for myopic astigmatism without iris registration, with iris registration, and with iris registration-assisted dynamic rotational eye tracking.

ABSTRACT

PURPOSE: To compare the visual and refractive outcomes of laser in situ keratomileusis (LASIK) without iris registration, with static preablation iris registration, and with preablation iris registration-assisted intra-ablation with dynamic rotational eye tracking. SETTING: Refractive Surgery Services, Dr. Agarwal's Eye Hospital, Chennai, India. DESIGN: Randomized clinical trial. METHODS: Eyes with myopic astigmatism (cylinder >1.00 diopter [D]) had LASIK using the Technolas 217z100 platform. Preoperative and postoperative assessment included uncorrected and corrected distance visual acuities, refraction, topographic analysis, and a routine LASIK workup. All cases were followed for 6 months. RESULTS: The mean spherical equivalent (SE) was -6.1 D ± 2.4 (SD) with no iris registration, -6.2 D ± 2.3 D with static iris registration, and -6.5 ± 2.2 D with dynamic iris registration (P=.4) preoperatively and -0.27 ± 0.4 D, -0.12 ± 0.4 D, and -0.02 ± 0.35 D, respectively, 6 months postoperatively (P < .001). The mean cylindrical error was -2.05 ± 0.7 D, -2.08 ± 0.5 D, and -2.13 ± 0.7 D, respectively, preoperatively (P=.6) and -0.37 ± 0.2 D, -0.29 ± 0.2 D, and -0.20 ± 0.3 D, respectively, at 6 months (P < .001). Alpins analysis showed comparable target and surgically induced astigmatism between the 3 groups; however, the difference vector, error angle, correction index, success index, and flattening index were best after dynamic iris registration (P < .001). CONCLUSIONS: In myopic astigmatism, iris registration with dynamic rotational eye tracking gave better results than iris registration alone or no iris registration. The worst outcomes were in cases without iris registration.