Chromatic Pupillometry to Assess the Melanopsin-Light Pathway in Progressive Supranuclear Palsy

The specific aim of this study is to investigate rod, cone and melanopsin driven pupillary light response in individuals with progressive supranuclear palsy (PSP), age-matched healthy controls and individuals with other neurodegenerative diseases using chromatic pupillometry, with special interest in assessing melanopsin-driven post-illumination pupil response (PIPR) as an identifier for PSP. The study addresses the following hypotheses: 1. Chromatic pupil responses, including rod/cone-driven rapid phase constriction and melanopsin-driven PIPR, are reduced in subjects with PSP compared to age-matched normal healthy control subjects, 2. Pupil parameters of the melanopsin-driven PIPR are abnormal in PSP subjects without supranuclear palsy, which is indicative of a subclinical physiological deficit of the OPN in the early stages of PSP. If these hypotheses are upheld, chromatic pupillometry to measure the PIPR promises to be a reliable in vivo, non-invasive, convenient and inexpensive technique to detect asymptomatic pupillomotor impairment in advance of diagnostic oculomotor signs and deterioration of cognitive function.