title: Objective analysis of toric intraocular lens rotation and centration.
abstract: OBJECTIVE
  To assess the repeatability of an objective image-analysis technique to determine intraocular lens (IOL) rotation and centration.
  
  
  METHODS
  Six European ophthalmology clinics.
  
  
  METHODS
  Eyes with an Akreos AO aspheric IOL with orientation marks were imaged. A masked observer rated image quality. The axis of rotation was determined from a line bisecting the IOL orientation marks. This was normalized for rotation of the eye between visits using the axis bisecting 2 consistent conjunctival vessels or iris features. The center of ovals overlaid to circumscribe the IOL optic edge and the pupil or limbus were compared to determine IOL centration. Intrasession repeatability was assessed in a subgroup of eyes and the variability of repeated analysis examined.
  
  
  RESULTS
  The SD of intrasession repeatability was +/-0.79 degrees for IOL rotational stability, +/-0.10 mm for horizontal centration, and +/-0.10 mm for vertical centration. The SD of repeated-analysis variability of the same image was +/-0.70 degrees, +/-0.20 mm, and +/-0.31 mm, respectively. The mean eye rotation (absolute) between visits was 2.23 degrees +/- 1.84 (SD) (10% >5 degrees rotation) using 1 set of consistent conjunctival vessels or iris features and 2.03 +/- 1.66 degrees (7%>5 degrees rotation) using the mean of 2 sets (P = .13). Poorer image quality resulted in larger apparent absolute IOL rotation (r = -0.45, P<.001).
  
  
  CONCLUSIONS
  Objective analysis of digital retroillumination images allowed sensitive assessment of IOL rotation and centration stability. Eye rotation between images can lead to significant errors if not taken into account. Image quality is important to analysis accuracy.
authors.affiliation: Aston University, School of Life and Health Sciences, Ophthalmic Research Group, Birmingham, United Kingdom. j.s.w.wolffsohn@aston.ac.uk
authors.forename: James S
authors.initials: JS
authors.lastname: Wolffsohn
authors.forename: Phillip J
authors.initials: PJ
authors.lastname: Buckhurst
mesh_terms: D001251:Astigmatism / Q000601:surgery; D001808:Blood Vessels / Q000033:anatomy & histology; D003228:Conjunctiva / Q000098:blood supply; D005133:Eye Movements / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007498:Iris / Q000033:anatomy & histology; D019654:Lens Implantation, Intraocular; D007910:Lenses, Intraocular; D009949:Orientation; D012399:Rotation; D014792:Visual Acuity / Q000502:physiology