An Evaluation of Two Candidate Functional Biomarkers for AMD

PURPOSE: 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.