title: Modulation transfer function of a toric intraocular lens: evaluation of the changes produced by rotation and tilt.
abstract: OBJECTIVE
  To evaluate the changes in optical quality when toric intraocular lenses (IOL) are rotated or tilted and to demonstrate that IOL rotation produces an increasing effect of aberrations.
  
  
  METHODS
  Modulation transfer function (MTF) and average modulation were used to analyze the image quality of a toric IOL. The axis of the toric IOL was rotated 5°, 10°, 15°, 20°, 25°, and 30° in successive MTF measurements. The tilt values were 0° to 5°, in increments of 1°, plus a tilt of 15°. Pupil diameters of 3 and 5 mm were used.
  
  
  RESULTS
  The MTF decay due to aberrations was more sensitive to rotation than tilt. The main decrement in the average modulation, of approximately 50% in both pupils, occurs when the IOL rotates from 0° to 5°. Between 0° and 1° tilt, the average modulation decreases approximately 25% for both pupils; with tilt >1°, the average modulation remains virtually unchanged. The points representing average modulation versus rotation angle are satisfactorily fitted by an exponential function, R=0.98. Average modulation versus tilt angle provides lower correlation degrees, R=0.91 and R=0.79, for 3- and 5-mm pupils, respectively.
  
  
  CONCLUSIONS
  The MTF of the toric IOL decays with rotation and tilt, with greater decrement occurring in rotation from 0° to 5°. An asymptotic value exists in the average modulation decay, meaning that for angles higher than 15°, the average modulation of the toric IOL remains virtually constant.
authors.affiliation: Fundación Oftalmológica del Mediterráneo and Departamento de Optica, Faculdad de Física, Universidad de Valencia, Valencia, Spain. Adelina.Felipe@uv.es
authors.forename: Adelina
authors.initials: A
authors.lastname: Felipe
authors.forename: José M
authors.initials: JM
authors.lastname: Artigas
authors.forename: Amparo
authors.initials: A
authors.lastname: Díez-Ajenjo
authors.forename: Carmen
authors.initials: C
authors.lastname: García-Domene
authors.forename: Cristina
authors.initials: C
authors.lastname: Peris
mesh_terms: D060437:Artificial Lens Implant Migration / Q000150:complications*; D057108:Corneal Wavefront Aberration / Q000209:etiology; D006801:Humans; D007910:Lenses, Intraocular; D008962:Models, Theoretical; D055095:Optics and Photonics; D012399:Rotation