title: Effect of posterior corneal astigmatism on power calculation and alignment of toric intraocular lenses: Comparison of methodologies.
abstract: OBJECTIVE
  To compare the accuracy of different methods that consider posterior corneal curvature in toric intraocular lens (IOL) calculations.
  
  
  METHODS
  Ein-Tal Eye Center, Tel-Aviv, Israel.
  
  
  METHODS
  Retrospective comparative case series.
  
  
  METHODS
  Consecutive cases of toric IOL implantation and preoperative measurements by optical biometry with optical low-coherence reflectometry (OLCR) (Lenstar LS 900) and a Scheimpflug camera (Pentacam) were retrospectively reviewed. Five methods of toric IOL calculation were compared as follows: (1) anterior corneal astigmatism using OLCR, (2) application of the Baylor nomogram, (3) posterior tomography combined with anterior corneal measurements using vector summation, (4) the Scheimpflug camera's true net power, and (5) total corneal refractive power. Toric IOL astigmatic power and axis, aiming for the lowest residual astigmatism, were selected according to these methods. Simulated residual refraction was calculated for each method based on manifest refraction and measured IOL alignment more than 3 weeks after surgery.
  
  
  RESULTS
  The study included 115 eyes of 92 patients. The median simulated residual astigmatism was lower when based on vector summation of anterior and posterior astigmatisms than with calculations based on anterior corneal measurements only, application of the Baylor nomogram, true net power, and total corneal refractive power readings (0.49 diopters [D] versus 0.70 D, 0.60 D, 0.64 D, and 0.76 D, respectively) (P < .001).
  
  
  CONCLUSIONS
  Residual astigmatism after toric IOL implantation can be reduced by appropriate consideration of the posterior corneal astigmatism. Using methods that take into account the effect of the posterior cornea in toric IOL calculations is suggested.
  
  
  BACKGROUND
  Drs. Assia and Kleinmann are consultants to Hanita Lenses, Israel. Dr. Abulafia received a speaker's fee from Haag-Streit AG. No other author has a financial or proprietary interest in any material or method mentioned.
authors.affiliation: From the Ein-Tal Eye Center (Reitblat, Levy, Kleinmann, Abulafia, Assia), Tel-Aviv, the Kaplan Medical Center (Kleinmann), Rehovot, affiliated with The Hebrew University, Jerusalem, the Assaf Harofeh Medical Center (Abulafia), Zerifin affiliated with Tel-Aviv University, Ramat Aviv, and the Meir Medical Center (Assia), Kfar-Saba, affiliated with Tel-Aviv University, Ramat Aviv, Israel. Electronic address: olga.reitblat@gmail.com.
authors.forename: Olga
authors.initials: O
authors.lastname: Reitblat
authors.affiliation: From the Ein-Tal Eye Center (Reitblat, Levy, Kleinmann, Abulafia, Assia), Tel-Aviv, the Kaplan Medical Center (Kleinmann), Rehovot, affiliated with The Hebrew University, Jerusalem, the Assaf Harofeh Medical Center (Abulafia), Zerifin affiliated with Tel-Aviv University, Ramat Aviv, and the Meir Medical Center (Assia), Kfar-Saba, affiliated with Tel-Aviv University, Ramat Aviv, Israel.
authors.forename: Adi
authors.initials: A
authors.lastname: Levy
authors.affiliation: From the Ein-Tal Eye Center (Reitblat, Levy, Kleinmann, Abulafia, Assia), Tel-Aviv, the Kaplan Medical Center (Kleinmann), Rehovot, affiliated with The Hebrew University, Jerusalem, the Assaf Harofeh Medical Center (Abulafia), Zerifin affiliated with Tel-Aviv University, Ramat Aviv, and the Meir Medical Center (Assia), Kfar-Saba, affiliated with Tel-Aviv University, Ramat Aviv, Israel.
authors.forename: Guy
authors.initials: G
authors.lastname: Kleinmann
authors.affiliation: From the Ein-Tal Eye Center (Reitblat, Levy, Kleinmann, Abulafia, Assia), Tel-Aviv, the Kaplan Medical Center (Kleinmann), Rehovot, affiliated with The Hebrew University, Jerusalem, the Assaf Harofeh Medical Center (Abulafia), Zerifin affiliated with Tel-Aviv University, Ramat Aviv, and the Meir Medical Center (Assia), Kfar-Saba, affiliated with Tel-Aviv University, Ramat Aviv, Israel.
authors.forename: Adi
authors.initials: A
authors.lastname: Abulafia
authors.affiliation: From the Ein-Tal Eye Center (Reitblat, Levy, Kleinmann, Abulafia, Assia), Tel-Aviv, the Kaplan Medical Center (Kleinmann), Rehovot, affiliated with The Hebrew University, Jerusalem, the Assaf Harofeh Medical Center (Abulafia), Zerifin affiliated with Tel-Aviv University, Ramat Aviv, and the Meir Medical Center (Assia), Kfar-Saba, affiliated with Tel-Aviv University, Ramat Aviv, Israel.
authors.forename: Ehud I
authors.initials: EI
authors.lastname: Assia
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001251:Astigmatism / Q000503:physiopathology*; D001699:Biometry / Q000379:methods; D003315:Cornea / Q000503:physiopathology*; D019781:Corneal Topography; D005260:Female; D006801:Humans; D019654:Lens Implantation, Intraocular / Q000379:methods*; D007910:Lenses, Intraocular; D008297:Male; D008875:Middle Aged; D049451:Nomograms; D055095:Optics and Photonics; D018918:Phacoemulsification; D019591:Pseudophakia / Q000503:physiopathology; D012029:Refraction, Ocular / Q000502:physiology; D012189:Retrospective Studies; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult