title: Toric intraocular lens orientation and residual refractive astigmatism: an analysis.
abstract: OBJECTIVE
  To analyze intraocular lens (IOL) orientation data from an online toric back-calculator (astigmatismfix.com) for determining if differences were apparent by lens type.
  
  
  METHODS
  A retrospective review of astigmatismfix.com toric back-calculations that included IOL identification and intended orientation axis.
  
  
  RESULTS
  Of 12,812 total validated calculation records, 8,229 included intended orientation and lens identification data. Of the latter, 5,674 calculations (69%) involved lenses oriented 5° or more from their intended position. Using estimated toric lens usage data, the percentage of lenses with orientation ≥5° from intended was 0.89% overall, but the percentage varied significantly between specific toric lens brands (P<0.05). The percentage of back-calculations related to lenses that were not oriented as intended was also statistically significantly different by lens brand (P<0.05). When IOLs were misoriented, they were significantly more likely to be misoriented in a counterclockwise direction (P<0.05). This was found to be due to a bias toward counterclockwise orientation observed with one specific brand, a bias that was not observed with the other three brands analyzed here.
  
  
  CONCLUSIONS
  The percentage of eyes with lens orientation ≥5° from intended in the Toric Results Analyzer data set was <1% of toric IOLs in general, with the relative percentage of Tecnis®Toric IOLs significantly higher than AcrySof®Toric IOLs. Both of these had higher rates than the Staar®Toric and Trulign®Toric lenses, with the availability of higher Tecnis and AcrySof cylinder powers a likely contributing factor. The AcrySof Toric IOL appears to be less likely than the Tecnis Toric IOL to cause residual astigmatism as a result of misorientation. The Tecnis Toric IOL appears more likely to be misoriented in a counterclockwise direction; no such bias was observed with the AcrySof Toric, the Trulign®Toric, or the Staar Toric IOLs.
authors.affiliation: Science in Vision, Akron, NY.
authors.forename: Rick
authors.initials: R
authors.lastname: Potvin
authors.affiliation: University of Iowa Carver College of Medicine, Iowa City, IA.
authors.forename: Brent A
authors.initials: BA
authors.lastname: Kramer
authors.affiliation: Minnesota Eye Consultants, Minnetonka, MN.
authors.forename: David R
authors.initials: DR
authors.lastname: Hardten
authors.affiliation: Vance Thompson Vision, Sioux Falls, SD, USA.
authors.forename: John P
authors.initials: JP
authors.lastname: Berdahl
keywords: AcrySof; Tecnis; cylinder; rotation; toric back-calculator