title: Validating a "pillar and collar" technique for measuring the edge lift of rigid contact lenses.
abstract: OBJECTIVE
  The clinical importance of the edge lift of rigid contact lenses is often neglected, possibly due to previous difficulties in its measurement. A new method of measuring axial edge lift (AEL) and radial edge lift (REL) using standard contact lens verification equipment, such as an optical spherometer, a thickness gauge, and contact lens V gauge, is described.
  
  
  METHODS
  The technique was validated for trueness (accuracy) and precision (repeatability) by measuring the edge lift of a number of monocurve lenses, manufactured both with and without a normal edge finish.
  
  
  RESULTS
  Edge lift was measured to an accuracy of 0.01 mm.
  
  
  CONCLUSIONS
  As long as a mean of eight independent measurements of back optic zone radius (BOZR), sagitta, and one measurement of center thickness are taken, the pillar and collar technique is capable of producing accurate and repeatable measurements of the edge lift of a rigid contact lens.
authors.affiliation: Department of Optometry, University of Bradford, West Yorkshire, United Kingdom.
authors.forename: W A
authors.initials: WA
authors.lastname: Douthwaite
authors.forename: M A
authors.initials: MA
authors.lastname: Hurst
mesh_terms: D003261:Contact Lenses / Q000592:standards; D003315:Cornea / Q000033:anatomy & histology; D006801:Humans; D019904:Polymethyl Methacrylate; D017755:Prosthesis Fitting; D015203:Reproducibility of Results
chemical_list: D019904:Polymethyl Methacrylate