title: 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: OBJECTIVE
  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.
  
  
  METHODS
  Refractive Surgery Services, Dr. Agarwal's Eye Hospital, Chennai, India.
  
  
  METHODS
  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.
authors.affiliation: Dr. Agarwal's Eye Hospital and Eye Research Centre, Chennai, India.
authors.forename: Gaurav
authors.initials: G
authors.lastname: Prakash
authors.forename: Amar
authors.initials: A
authors.lastname: Agarwal
authors.forename: Dhivya
authors.initials: D
authors.lastname: Ashok Kumar
authors.forename: Soosan
authors.initials: S
authors.lastname: Jacob
authors.forename: Athiya
authors.initials: A
authors.lastname: Agarwal
mesh_terms: D001251:Astigmatism / Q000601:surgery*; D019781:Corneal Topography; D005128:Eye Diseases / Q000503:physiopathology; D005133:Eye Movements / Q000502:physiology; D006801:Humans; D007498:Iris / Q000502:physiology*; D020731:Keratomileusis, Laser In Situ; D054018:Lasers, Excimer / Q000627:therapeutic use*; D009216:Myopia / Q000601:surgery*; D012029:Refraction, Ocular / Q000502:physiology; D014102:Torsion Abnormality / Q000503:physiopathology; D016896:Treatment Outcome; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult