title: Development of a program for toric intraocular lens calculation considering posterior corneal astigmatism, incision-induced posterior corneal astigmatism, and effective lens position.
abstract: BACKGROUND
  To evaluate the toric intraocular lens (IOL) calculation considering posterior corneal astigmatism, incision-induced posterior corneal astigmatism, and effective lens position (ELP).
  
  
  METHODS
  Two thousand samples of corneal parameters with keratometric astigmatism ≥ 1.0 D were obtained using bootstrap methods. The probability distributions for incision-induced keratometric and posterior corneal astigmatisms, as well as ELP were estimated from the literature review. The predicted residual astigmatism error using method D with an IOL add power calculator (IAPC) was compared with those derived using methods A, B, and C through Monte-Carlo simulation. Method A considered the keratometric astigmatism and incision-induced keratometric astigmatism, method B considered posterior corneal astigmatism in addition to the A method, method C considered incision-induced posterior corneal astigmatism in addition to the B method, and method D considered ELP in addition to the C method. To verify the IAPC used in this study, the predicted toric IOL cylinder power and its axis using the IAPC were compared with ray-tracing simulation results.
  
  
  RESULTS
  The median magnitude of the predicted residual astigmatism error using method D (0.25 diopters [D]) was smaller than that derived using methods A (0.42 D), B (0.38 D), and C (0.28 D) respectively. Linear regression analysis indicated that the predicted toric IOL cylinder power and its axis had excellent goodness-of-fit between the IAPC and ray-tracing simulation.
  
  
  CONCLUSIONS
  The IAPC is a simple but accurate method for predicting the toric IOL cylinder power and its axis considering posterior corneal astigmatism, incision-induced posterior corneal astigmatism, and ELP.
authors.affiliation: Department of Ophthalmology, Korea University College of Medicine, Seoul, South Korea.
authors.forename: Youngsub
authors.initials: Y
authors.lastname: Eom
authors.affiliation: Space Optics Laboratory, Department of Astronomy, Yonsei University, Seoul, South Korea.|Center for Galaxy Evolution Research, Yonsei University, Seoul, South Korea.|Yonsei University Observatory, Yonsei University, Seoul, South Korea.
authors.forename: Dongok
authors.initials: D
authors.lastname: Ryu
authors.affiliation: College of Optical Sciences, University of Arizona, Tucson, AZ, USA.
authors.forename: Dae Wook
authors.initials: DW
authors.lastname: Kim
authors.affiliation: Space Optics Laboratory, Department of Astronomy, Yonsei University, Seoul, South Korea.|Center for Galaxy Evolution Research, Yonsei University, Seoul, South Korea.|Yonsei University Observatory, Yonsei University, Seoul, South Korea.
authors.forename: Seul Ki
authors.initials: SK
authors.lastname: Yang
authors.affiliation: Department of Ophthalmology, Korea University College of Medicine, Seoul, South Korea.
authors.forename: Jong Suk
authors.initials: JS
authors.lastname: Song
authors.affiliation: Space Optics Laboratory, Department of Astronomy, Yonsei University, Seoul, South Korea.|Center for Galaxy Evolution Research, Yonsei University, Seoul, South Korea.|Yonsei University Observatory, Yonsei University, Seoul, South Korea.
authors.forename: Sug-Whan
authors.initials: SW
authors.lastname: Kim
authors.affiliation: Department of Ophthalmology, Korea University College of Medicine, Seoul, South Korea. hyomkim@kumc.or.kr.
authors.forename: Hyo Myung
authors.initials: HM
authors.lastname: Kim
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000175:diagnosis* / Q000209:etiology; D001699:Biometry / Q000379:methods; D002387:Cataract Extraction; D003315:Cornea / Q000503:physiopathology* / Q000601:surgery; D019781:Corneal Topography; D005260:Female; D006801:Humans; D019654:Lens Implantation, Intraocular; D007910:Lenses, Intraocular; D008297:Male; D009010:Monte Carlo Method; D049451:Nomograms; D055095:Optics and Photonics; D011183:Postoperative Complications; D012029:Refraction, Ocular; D012189:Retrospective Studies
keywords: Effective lens position; Posterior corneal astigmatism, Incision-induced astigmatism; Toric intraocular lens