Differences between PLR findings in published papers and our work may be related to the study population (AD risk vs. AD patients) and pupillometry method, i.e. full field white or chromatic light stimuli vs. focal red and blue stimuli that enables to assess rod, cone and melanopsin mediated PLR at central and peripheral retinal locations, as well as the advancement in capturing the pupil response. This evidence concerns the gene OPN4 and Alzheimer disease.