Pupillometric evaluation and analysis of light reflex in healthy subjects as a tool to study autonomic nervous system changes with aging

To assess the relationships between aging and autonomic control of pupillary functions, TV-pupillometry and light reflex evaluation were performed in 52 healthy volunteers in the age range 15-75 years, grouped into four age classes (group 1: 15-29 years, Group 2: 30-44 years, Group 3: 45-59 years, Group 4: 60-75 years). Baseline light pupil diameter was found to be age-dependent, together with light reflex contraction velocity, which presented a linear correlation with age. Light reflex amplitude and half-redilatation velocity were reduced in older subjects, but presented only a weak linear correlation with age, while latency, contraction time and half-redilatation time percent of secondary dilatation and redilatation at 5 seconds did not show significant changes with age. These results confirm that there are important age-dependent changes in the mechanisms involved in pupillary autonomic functions, regarding both sympathetic and parasympathetic components. These changes appear to be easily detectable by making use of a sensitive and non-invasive technique such as TV-pupillometry.