title: Influence of corneal asphericity on the refractive outcome of intraocular lens implantation in cataract surgery.
abstract: OBJECTIVE
  To evaluate the possible influence of anterior corneal surface asphericity on the refractive outcomes in eyes having intraocular lens (IOL) implantation after cataract surgery.
  
  
  METHODS
  Fondazione G.B. Bietti IRCCS, Rome, Italy.
  
  
  METHODS
  Retrospective comparative case series.
  
  
  METHODS
  Intraocular lens power was calculated using the Haigis, Hoffer Q, Holladay 1, and SRK/T formulas. Asphericity (Q-value) was measured at 8.0 mm with a Placido-disk corneal topographer (Keratron), a rotating Scheimpflug camera (Pentacam), and a rotating Scheimpflug camera combined with Placido-disk corneal topography (Sirius). The relationship between the error in refraction prediction (ie, difference between expected refraction and refraction measured 1 month after surgery) and the Q-value was assessed by linear regression.
  
  
  RESULTS
  The same IOL model (Acrysof SA60AT) was implanted in 115 eyes of 115 consecutive patients. Regression analysis showed a statistically significant relationship between the error in refraction prediction and the Q-value with all formulas and all devices. In all cases, a more negative Q-value (prolate cornea) was associated with a myopic outcome, whereas a more positive Q-value (oblate cornea) was associated with a hyperopic outcome. The highest coefficient of determination was detected between the Hoffer Q formula and the Placido-disk corneal topographer (R(2) = 0.2630), for which the error in refraction prediction (y) was related to the Q-value (x) according to the formula y = -0.2641 + 1.4589 × x.
  
  
  CONCLUSIONS
  Corneal asphericity influences the refractive outcomes of IOL implantation and should be taken into consideration when using third-generation IOL power formulas.
  
  
  BACKGROUND
  Dr. Hoffer receives book royalties from Slack, Inc., Thorofare, New Jersey, and formula royalties from all manufacturers using the Hoffer Q formula. No other author has a financial or proprietary interest in any material or method mentioned.
authors.affiliation: From the Fondazione G.B. Bietti IRCCS (Savini), Rome, Studio Oculistico d'Azeglio (Barboni), Bologna, and the Scientific Institute San Raffaele (Barboni), Milan, Italy; the Stein Eye Institute (Hoffer), University of California, and St. Mary's Eye Center (Hoffer), Santa Monica, California, USA. Electronic address: giacomo.savini@alice.it.
authors.forename: Giacomo
authors.initials: G
authors.lastname: Savini
authors.affiliation: From the Fondazione G.B. Bietti IRCCS (Savini), Rome, Studio Oculistico d'Azeglio (Barboni), Bologna, and the Scientific Institute San Raffaele (Barboni), Milan, Italy; the Stein Eye Institute (Hoffer), University of California, and St. Mary's Eye Center (Hoffer), Santa Monica, California, USA.
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Hoffer
authors.affiliation: From the Fondazione G.B. Bietti IRCCS (Savini), Rome, Studio Oculistico d'Azeglio (Barboni), Bologna, and the Scientific Institute San Raffaele (Barboni), Milan, Italy; the Stein Eye Institute (Hoffer), University of California, and St. Mary's Eye Center (Hoffer), Santa Monica, California, USA.
authors.forename: Piero
authors.initials: P
authors.lastname: Barboni
mesh_terms: D058452:Axial Length, Eye; D001699:Biometry; D003315:Cornea / Q000473:pathology*; D019781:Corneal Topography; D006801:Humans; D019654:Lens Implantation, Intraocular; D007910:Lenses, Intraocular; D055095:Optics and Photonics; D018918:Phacoemulsification; D012029:Refraction, Ocular / Q000502:physiology*; D012030:Refractive Errors / Q000175:diagnosis; D012189:Retrospective Studies