title: Correlation of Back Optic Zone Radius measurement of rigid contact lenses with radiuscope and keratometer.
abstract: OBJECTIVE
  To investigate the accuracy of Back Optic Zone Radius (BOZR, base curve) measurements with manual keratometer for spherical polymethylmethacrylate (PMMA) lenses.
  
  
  METHODS
  100 spherical PMMA contact lenses were selected randomly from the trial sets. One investigator measured the BOZR with radiuscope. The second investigator measured the BOZR with keratometer. The two investigators were masked to each other's readings. As the keratometer is designed to measure a convex corneal surface, the BOZR readings are less than actual radii. A correction factor of 0.025 was used to have corrected keratometers readings.
  
  
  RESULTS
  There was a high correlation between the BOZR measurement with radiuscope and the uncorrected (Pearson's correlation coefficient, r=0.99) and corrected (r=0.99) measurements with keratometer. The mean difference between BOZR measurement with radiuscope and the uncorrected and corrected measurements with keratometer were 0.003 mm (p=0.62) and -0.024 mm (p<0.001) respectively. The 95% limits of agreement for the BOZR measurements with radiuscope and the uncorrected and corrected measurements with keratometer were -0.11 to 0.11 mm and -0.14 to 0.09 mm respectively.
  
  
  CONCLUSIONS
  We found that the uncorrected BOZR measurements with keratometer were similar to the BOZR measurements with radiuscope. With unavailability of radiuscope in majority of contact lens practice, keratometer can be used to measure the BOZR of contact lenses.
authors.affiliation: L V Prasad Eye Institute, Banjara Hills, Hyderabad, AP, India.
authors.forename: Tukaram
authors.initials: T
authors.lastname: Kumbar
authors.forename: T
authors.initials: T
authors.lastname: Shyam Sunder
authors.forename: Jawalkar
authors.initials: J
authors.lastname: Swati
authors.forename: Asma
authors.initials: A
authors.lastname: Fathima
authors.forename: U K
authors.initials: UK
authors.lastname: Addepally
authors.forename: Harsha L
authors.initials: HL
authors.lastname: Rao
authors.forename: Varsha M
authors.initials: VM
authors.lastname: Rathi
mesh_terms: D003261:Contact Lenses; D004867:Equipment Design; D019544:Equipment Failure Analysis; D019904:Polymethyl Methacrylate / Q000737:chemistry*; D012031:Refractometry / Q000295:instrumentation*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D019904:Polymethyl Methacrylate