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

PurposeTo 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.SettingRefractive Surgery Services, Dr. Agarwal’s Eye Hospital, Chennai, India.DesignRandomized clinical trial.MethodsEyes 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.ResultsThe 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).ConclusionsIn 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.Financial DisclosureNo author has a financial or proprietary interest in any material or method mentioned. Additional disclosures are found in the footnotes.