title: An evaluation of two candidate functional biomarkers for AMD.
abstract: OBJECTIVE
  To evaluate the intersession repeatability of the Colour Assessment and Diagnosis (CAD) test and a novel 14-Hz flicker test in a population of healthy participants to provide benchmark data for their use as functional biomarkers for age-related macular degeneration (AMD).
  
  
  METHODS
  Visual function was assessed using both techniques in 30 healthy adults (mean [standard deviation] age 36.3 [14.1] years) on two separate days. Intersession repeatability of RG and YB CAD thresholds and 14-Hz flicker thresholds was assessed by determining their coefficient of repeatability (CoR).
  
  
  RESULTS
  The CoR was calculated to be 0.39 CAD units (17.0%) for RG thresholds, 0.43 CAD units (31.1%) for YB thresholds, and 0.015 (53.4%) for 14-Hz flicker contrast thresholds. On average, thresholds improved by 4.72% (RG), 6.33% (YB), and 13.3% (14-Hz flicker) between visits 1 and 2, suggesting a small but consistent learning effect. The CoR for all parameters was relatively small compared to the mean thresholds obtained (RG: mean 2.27 [4.58], CoR 0.39; YB: mean 1.37 [0.55], CoR 0.43; 14-Hz flicker: mean 0.028 [0.01], CoR 0.015).
  
  
  CONCLUSIONS
  This study has described the repeatability of the CAD and 14-Hz flicker tests. These data can help clinicians decide if the results from repeated measures are of clinical significance. Despite pretest training, there was some evidence of a learning effect. Therefore, clinical trials using these techniques should ensure training is sufficient to minimize these effects.
authors: *BSc(Hons) †PhD, BSc(Hons) School of Optometry and Vision Sciences, Cardiff University, Cardiff, Wales (CMc, THM), and School of Health Sciences, City University London, London, England (AMB), United Kingdom.
authors: Claire
authors: C
authors: McKeague
authors: Alison M
authors: AM
authors: Binns
authors: Tom H
authors: TH
authors: Margrain
mesh_terms: D000328:Adult; D000368:Aged; D055253:Color Vision / Q000502:physiology*; D015350:Contrast Sensitivity / Q000502:physiology; D005260:Female; D005425:Flicker Fusion / Q000502:physiology*; D064368:Healthy Volunteers; D006801:Humans; D008268:Macular Degeneration / Q000175:diagnosis* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011601:Psychophysics; D015203:Reproducibility of Results; D012160:Retina / Q000502:physiology*; D014787:Vision Tests / Q000379:methods*; D055815:Young Adult