title: Clinical and experimental validation of a slit lamp modification to measure toric lens position.
abstract: OBJECTIVE
  A simple novel slit lamp beam angular scale modification is described to allow more accurate measurement of toric contact and intraocular lens position.
  
  
  METHODS
  The modified slit lamp measuring technique was validated in both an experimental and a clinical setting, with two independent observers. The device was tested against a known reference source, and intraobserver variability in a clinical setting measuring toric intraocular lens (IOL) position was ascertained.
  
  
  RESULTS
  In the experimental setting 80 paired observations were analysed. Mean variance was 0.19° (95% CI 0.01-0.37), with a typical measurement error of 0.49°. Intraobserver variation had variance of -0.03° (95% CI -0.2 to 0.15) with a typical error of 0.47°. Clinical assessment of toric IOL position was made in 21 eyes. For this group, intraobserver variation had variance of -0.1° (95% CI -0.281 to 0.62) with a typical error of 1.36°. Intraclass correlation coefficient for all measures was 1.0.
  
  
  CONCLUSIONS
  This simple technique has sufficient precision to be valuable in the clinical setting where photographic techniques may not be available or practical.
authors.affiliation: Cardiff Eye Unit and Princess of Wales Hospital, 19 Glan Rhymni, Wales, Cardiff CF24 2TW, UK. hatch.mukherjee@gmail.com
authors.forename: Achyut N
authors.initials: AN
authors.lastname: Mukherjee
authors.forename: Chunwah
authors.initials: C
authors.lastname: So
authors.forename: Vinod
authors.initials: V
authors.lastname: Kumar
mesh_terms: D001251:Astigmatism / Q000628:therapy; D002387:Cataract Extraction; D003263:Contact Lenses, Hydrophilic; D003941:Diagnostic Techniques, Ophthalmological / Q000295:instrumentation*; D006801:Humans; D019654:Lens Implantation, Intraocular; D007910:Lenses, Intraocular; D015588:Observer Variation