title: Reliability of a Single Light Source Purkinjemeter in Pseudophakic Eyes.
abstract: OBJECTIVE
  To study the reliability of Purkinje image analysis for assessment of intraocular lens tilt and decentration in pseudophakic eyes.
  
  
  METHODS
  The study comprised 64 eyes of 39 patients. All eyes underwent phacoemulsification with intraocular lens implanted in the capsular bag. Lens decentration and tilt were measured multiple times by an infrared Purkinjemeter. A total of 396 measurements were performed 1 week and 1 month postoperatively. Lens tilt (Tx, Ty) and decentration (Dx, Dy) in horizontal and vertical directions, respectively, were calculated by dedicated software based on regression analysis for each measurement using only four images, and afterward, the data were averaged (mean values, MV) for repeated sequence of measurements. New software was designed by us for recalculating lens misalignment parameters offline, using a complete set of Purkinje images obtained through the repeated measurements (9 to 15 Purkinje images) (recalculated values, MV'). MV and MV' were compared using SPSS statistical software package.
  
  
  RESULTS
  MV and MV' were found to be highly correlated for the Tx and Ty parameters (R2 > 0.9; p < 0.001), moderately correlated for the Dx parameter (R2 > 0.7; p < 0.001), and weakly correlated for the Dy parameter (R2 = 0.23; p < 0.05). Reliability was high (Cronbach α > 0.9) for all measured parameters. Standard deviation values were 0.86 ± 0.69 degrees, 0.72 ± 0.65 degrees, 0.04 ± 0.05 mm, and 0.23 ± 0.34 mm for Tx, Ty, Dx, and Dy, respectively.
  
  
  CONCLUSIONS
  The Purkinjemeter demonstrated high reliability and reproducibility for lens misalignment parameters. To further improve reliability, we recommend capturing at least six Purkinje images instead of three.
authors.affiliation: *PhD †MD ‡MD, PhD Institute of Experimental Ophthalmology, Saarland University, Homburg/Saar, Germany (EJ, EC, AL); Department of Ophthalmology, Saarland University Medical Center, Homburg/Saar, Germany (EC, BS); and Section of Neurobiology of the Eye, Institute for Ophthalmic Research, University of Tübingen, Tübingen, Germany (FS).
authors.forename: Edgar
authors.initials: E
authors.lastname: Janunts
authors.forename: Ekaterina
authors.initials: E
authors.lastname: Chashchina
authors.forename: Berthold
authors.initials: B
authors.lastname: Seitz
authors.forename: Frank
authors.initials: F
authors.lastname: Schaeffel
authors.forename: Achim
authors.initials: A
authors.lastname: Langenbucher
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D060437:Artificial Lens Implant Migration / Q000175:diagnosis*; D003941:Diagnostic Techniques, Ophthalmological / Q000295:instrumentation*; D005260:Female; D006801:Humans; D019654:Lens Implantation, Intraocular; D007910:Lenses, Intraocular; D008027:Light; D008297:Male; D008875:Middle Aged; D018918:Phacoemulsification; D019591:Pseudophakia / Q000150:complications*; D015203:Reproducibility of Results