title: The validity and repeatability of the New Aniseikonia Test.
abstract: OBJECTIVE
  Aniseikonia has been traditionally measured using the New Aniseikonia Test (NAT) based on red/green anaglyphs. This study was designed to establish whether the NAT is a valid and reliable test.
  
  
  METHODS
  The NAT was tested on three groups of subjects: a control group (n = 45) and two groups of participants at risk of experiencing aniseikonia, those with anisometropia greater than or equal to 1.00 D (n = 29) and those with bilateral pseudophakia (n = 26). The validity of the test was established by comparing the measured aniseikonia with that simulated with size lenses in a double-blind study. Repeatability was evaluated by comparing the results obtained at two different time points.
  
  
  RESULTS
  Our results indicate that the NAT underestimates aniseikonia and more so in the horizontal than in the vertical direction. Repeatability was poor, although biases were clinically insignificant. However, the 95% limits of agreement were around +/-2%. The behavior of the test was similar in the three groups of subjects.
  
  
  CONCLUSIONS
  We conclude that the repeatability of the NAT is not very high and recommend that clinicians be cautious when interpreting the results of this test.
authors.affiliation: Departamento de Optica II (Optometria y Vision), Universidad Complutense, Madrid, Spain. bantona@opt.ucm.es
authors.forename: Beatriz
authors.initials: B
authors.lastname: Antona
authors.forename: Francisco
authors.initials: F
authors.lastname: Barra
authors.forename: Ana
authors.initials: A
authors.lastname: Barrio
authors.forename: Enrique
authors.initials: E
authors.lastname: Gonzalez
authors.forename: Isabel
authors.initials: I
authors.lastname: Sánchez
mesh_terms: D000328:Adult; D000839:Aniseikonia / Q000175:diagnosis* / Q000503:physiopathology; D006801:Humans; D012029:Refraction, Ocular / Q000502:physiology; D015203:Reproducibility of Results; D014787:Vision Tests / Q000592:standards*; D015348:Vision, Binocular / Q000502:physiology