Online Appendix Macular Pigment Optical Density (MPOD) Testing in the Elderly: Development of a Simplified and Abbreviated Testing Protocol to Minimize Fatigue and Participant Burden

The most commonly and most extensively validated method used to measure MPOD is a psychophysical test based on heterochromatic flicker photometry (HFP). 2 This method determines psychophysically the ratio between the visual sensitivity for a flickering test light that is maximally absorbed by MPs alternating in counterphase with a suppressing background at a wavelength that is not absorbed by the MP. The ratio between two measurements, one at the fovea and one parafoveally (where the MP density is minimal) provides an estimate of the MPOD. Subjects taking the test with this technique are asked to find the point at which the sensation of flicker disappears typically by adjusting a knob that controls the intensity of the flickering test target. The range of intensity within which flicker is no longer appreciated –also termed the “no-flicker zone”– varies in width with the rate at which the test target is flickering, such that the flickering frequency needs to be individually optimized based on an initial determination of the subject’s flicker fusion frequency and subsequent fine-tunings performed by the examiner. As previously reported, subjects undergoing MPOD determinations are typically asked to identify empirically the middle of the no-flicker zone with progressively finer adjustments of the knob and to push a button at the subjectively determined point. Figure S1 illustrates the testing apparatus used in our study (Macular Metrics Corp., Rehoboth, MA). The appearance of the test targets from a participant’s perspective is illustrated in Panels C and D. By using this testing protocol typically used in younger adults, our initial experience in the older adults (mean age 79) participanting in ARMA was that of