title: The Effect of Lens Sphere and Cylinder Power on Residual Astigmatism and Its Resolution After Toric Intraocular Lens Implantation.
abstract: OBJECTIVE
  To analyze correlations between residual refractive cylinder (and its correction through lens reorientation) with the sphere and cylinder power of the toric intraocular lens (IOL) implanted.
  
  
  METHODS
  An online toric back-calculator (www.astigmatismfix.com) allows users to input toric IOL planning data, along with postoperative IOL orientation and refractive results; these data are used to determine the optimal orientation of the IOL to reduce refractive astigmatism. This was a retrospective data analysis; aggregate historical data were extracted from this calculator to investigate the relationship between residual refractive astigmatism and IOL cylinder and sphere power.
  
  
  RESULTS
  A total of 12,812 records, 4,619 of which included IOL sphere power, were available for analysis. There was no significant effect of sphere power on residual refractive astigmatism (P = .25), but lower IOL cylinder powers were associated with significantly lower residual refractive astigmatism (P < .05). The difference between the intended and ideal orientation was higher in the lower IOL cylinder power groups (P < .01). Overcorrection of astigmatism was significantly more likely with higher IOL cylinder power (P < .01), but not with sphere power (P = .33). Reorientation to correct residual refractive cylinder to less than 0.50 diopters (D) was more successful with IOL cylinder powers of 1.50 D or less (P < .01); IOL sphere power had no apparent effect.
  
  
  CONCLUSIONS
  There were significant effects of IOL cylinder power on residual refractive astigmatism, the difference between intended and ideal orientation, the likelihood of overcorrection, and the likelihood of astigmatism reduction with lens reorientation. IOL sphere power appeared to have no such effects. [J Refract Surg. 2017;33(3):157-162.].
authors.forename: John P
authors.initials: JP
authors.lastname: Berdahl
authors.forename: David R
authors.initials: DR
authors.lastname: Hardten
authors.forename: Brent A
authors.initials: BA
authors.lastname: Kramer
authors.forename: Richard
authors.initials: R
authors.lastname: Potvin
mesh_terms: D001251:Astigmatism / Q000209:etiology / Q000503:physiopathology / Q000628:therapy*; D006801:Humans; D019654:Lens Implantation, Intraocular; D007910:Lenses, Intraocular / Q000009:adverse effects*; D055095:Optics and Photonics; D011184:Postoperative Period; D011474:Prosthesis Design; D012029:Refraction, Ocular / Q000502:physiology*; D012189:Retrospective Studies