title: Reliability of power profiles measured on NIMO TR1504 (Lambda-X) and effects of lens decentration for single vision, bifocal and multifocal contact lenses.
abstract: OBJECTIVE
  To evaluate the repeatability of power profiles measured on NIMO TR1504 (Lambda-X, Belgium) and investigate the effects of lens decentration on the power profiles for single vision (SV), bifocal (BF) and multifocal (MF) contact lenses.
  
  
  METHODS
  Accuracy of the sphere power was evaluated using single vision BK-7 calibration glass lenses of six minus and six plus powers. Three SV and four BF/MF contact lenses - three lenses each, were measured five times to calculate the coefficients of repeatability (COR) of the instrument. The COR was computed for each chord position, lens design, prescription power and operator. One lens from each type was measured with a deliberate decentration up to ±0.5mm in 0.1mm steps.
  
  
  RESULTS
  For all lenses, the COR varied across different regions of the half-chord position. In general, SV lenses showed lower COR compared to the BF/MF group lenses. There were no noticeable trends of COR between prescription powers for SV and BF/MF lenses. The shape of the power profiles was not affected when lenses were deliberately decentered for all SV and PureVision MF lenses. However, for Acuvue BF lenses, the peak to trough amplitude of the power profiles flattened up to 1.00D.
  
  
  CONCLUSIONS
  The COR across the half-chord of the optic zone diameter was mostly within clinical relevance except for the central 0.5mm half-chord position. COR were dependent on the lens type, whereby BF/MF group produced higher COR than SV lenses. The effects of deliberate decentration on the shape of power profiles were pronounced for lenses where the profiles had sharp transitions of power.
authors.affiliation: Brien Holden Vision Institute, Sydney, Australia. Electronic address: e.kim@brienholdenvision.org.
authors.forename: Eon
authors.initials: E
authors.lastname: Kim
authors.affiliation: Brien Holden Vision Institute, Sydney, Australia.
authors.forename: Ravi C
authors.initials: RC
authors.lastname: Bakaraju
authors.affiliation: Brien Holden Vision Institute, Sydney, Australia; Vision CRC, Sydney, Australia; School of Optometry and Vision Science, University of New South Wales, Sydney, Australia.
authors.forename: Klaus
authors.initials: K
authors.lastname: Ehrmann
mesh_terms: D003261:Contact Lenses; D004867:Equipment Design; D006801:Humans; D009907:Optometry / Q000295:instrumentation*; D011305:Presbyopia; D012029:Refraction, Ocular / Q000502:physiology*; D015203:Reproducibility of Results
keywords: Contact lenses; Lentes de contacto; Monofocales; Multifocales; Multifocals; NIMO; NIMO TR1504; Perfil de potencia; Power profile; Repeatability; Repetibilidad