title: Effect of Iris registration on visual outcome in wavefront-guided LASEK for myopic astigmatism.
abstract: OBJECTIVE
  This study aimed to investigate the effect of iris registration (IR) on visual outcomes in wavefront-guided LASEK for myopic astigmatism.
  
  
  METHODS
  The retrospective chart review was performed for wavefront-guided LASEK using VISX Star S4 in patients with myopic astigmatism (cylinder ≥ 1.00 diopter[D]). Eyes were divided into IR group (LASEK with IR at the time of surgery) and Non-IR group (LASEK without IR system + failed-IR engagement during LASEK). Visual acuity (VA), astigmatism, higher-order aberration (HOA), and contrast sensitivity were assessed preoperatively and 3 months postoperatively. The IR and Non-IR groups were subcategorized depending on the spherical equivalent (lower myopia ≤-5.00 D vs. higher myopia >-5.00 D) for the comparison of HOA changes.
  
  
  RESULTS
  Postoperative uncorrected VAs showed no differences between IR (n = 30) and Non-IR (n = 46). In astigmatic vector analyses, no differences were noted in the mean magnitude of error and the mean angle of error between two groups. There were no differences in postoperative total HOA, spherical aberration (SA), coma, and trefoil between the groups, either. The total HOA and SA increased in both groups, while coma increased only in Non-IR. In higher myopia, ΔRMS of coma was smaller in IR. Preoperative and postoperative total HOA were linearly correlated in Non-IR, but not for IR. Contrast sensitivity of 12 cycles per degree improved in both groups.
  
  
  CONCLUSIONS
  IR had similar outcomes to conventional trackers in wavefront-guided LASEK, with less tendency of inducing coma, especially in higher myopia.
authors.affiliation: Department of Ophthalmology, Chungnam National University School of Medicine, Daejeon, Republic of Korea.
authors.forename: Jong Joo
authors.initials: JJ
authors.lastname: Lee
authors.affiliation: Department of Ophthalmology, Seoul National University College of Medicine, 103 Daehak-ro, Jongno-gu, Seoul, 03080, Republic of Korea. kmk9@snu.ac.kr.|Laboratory of Ocular Regenerative Medicine and Immunology, Seoul Artificial Eye Center, Seoul National University Hospital Biomedical Research Institute, Seoul, Republic of Korea. kmk9@snu.ac.kr.
authors.forename: Mee Kum
authors.initials: MK
authors.lastname: Kim
authors.affiliation: Department of Ophthalmology, Seoul National University College of Medicine, 103 Daehak-ro, Jongno-gu, Seoul, 03080, Republic of Korea.|Laboratory of Ocular Regenerative Medicine and Immunology, Seoul Artificial Eye Center, Seoul National University Hospital Biomedical Research Institute, Seoul, Republic of Korea.
authors.forename: Won Ryang
authors.initials: WR
authors.lastname: Wee
mesh_terms: D000293:Adolescent; D000328:Adult; D001251:Astigmatism / Q000503:physiopathology / Q000601:surgery*; D015350:Contrast Sensitivity / Q000502:physiology; D057108:Corneal Wavefront Aberration / Q000473:pathology; D005260:Female; D006801:Humans; D049008:Keratectomy, Subepithelial, Laser-Assisted / Q000379:methods*; D008297:Male; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D012189:Retrospective Studies; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult
keywords: Astigmatism; Higher-order aberration; Iris registration; LASEK; Wavefront