title: A freely accessible, evidence based, objective system of analysis of posterior capsular opacification; evidence for its validity and reliability.
abstract: BACKGROUND
  The aim of this study was to develop a system of computerised analysis of digital images of posterior capsule opacification (PCO) that is evidence based, objective and freely available. The paper will present evidence for the reliability and validity of the developed system.
  
  
  METHODS
  The system of PCO analysis was developed considering current published evidence on visual significance of PCO and additional investigative analysis of PCO images. Details of the image processing and analysis steps are discussed and a final system that measures an entropy score weighted toward proximity to central areas is described. In order to assess validity, the systems ability to measure PCO progression is assessed along with the visual significance of its final computerised scores. Reliability of the system is also assessed.
  
  
  RESULTS
  The final system runs successfully and is simple to use. Analyses of PCO by the system show an ability to detect early progression of PCO as well as detection of visually significant PCO. Images with no clinical PCO produce very low scores in the analysis. Reliability of the system of analysis is shown to be satisfactory.
  
  
  CONCLUSIONS
  This paper presents a system of PCO analysis that is evidence based, objective and clinically useful. Substantial evidence is provided for its validity and reliability.
authors.affiliation: Manchester Eye Hospital, UK. TAslam@AOL.COM
authors.forename: Tariq M
authors.initials: TM
authors.lastname: Aslam
authors.forename: Niall
authors.initials: N
authors.lastname: Patton
authors.forename: Jim
authors.initials: J
authors.lastname: Graham
mesh_terms: D022126:Access to Information; D002386:Cataract / Q000175:diagnosis*; D003941:Diagnostic Techniques, Ophthalmological; D019317:Evidence-Based Medicine; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D007903:Lens Capsule, Crystalline / Q000473:pathology*; D011183:Postoperative Complications; D015203:Reproducibility of Results; D012984:Software