Method to quickly map multifocal Pupillary Response Fields (mPRF) using Frequency Tagging

We present a method for mapping multifocal Pupillary Response Fields in a short amount of time, using a visual stimulus covering 40{degrees} of visual angle, divided in 9 contiguous sectors, simultaneously modulated in luminance at specific, incommensurate, temporal frequencies. We tested this multiple Pupillary Frequency Tagging (mPFT) approach with young healthy participants (N=36), and show that the spectral power of the sustained pupillary response elicited by 45 seconds of fixation of this multipartite stimulus reflects the relative contribution of each sector/frequency to the overall pupillary response. We further analyze the phase lag for each temporal frequency as well as several global features related to pupil state. Test retest performed on a subset of participants indicates good repeatability. We also investigate the existence of structural (RNFL)/functional (mPFT) relationships. We then summarize results of clinical studies conducted with mPFT on patients with neuropathies and retinopathies and show that the features derived from pupillary signal analyzes, the distribution of spectral power in particular, allows sorting patients from healthy participants with excellent sensitivity and specificity. This method thus appears a convenient, objective and fast tool for assessing the integrity of retino-pupillary circuits, as well as idiosyncrasies, that permits to objectively detect or follow-up retinopathies or neuropathies in a short amount of time.