Relationship between age, sex and pupillary unrest

Pupllary unrest in ambient light (PUAL) is the chaotic fluctuation of pupil diameter about its mean value. The degree of fluctuation is typically measured using a pupillometer and quantified using an index that sums fluctuations in a frequency range of interest. Indices that measure PUAL show promise in predicting effects of sedative or opioid drugs. Because PUAL is mediated by the parasympathetic nervous system, it would be expected to decline with age-related decreases in parasympathetic tone. In this study we measured average PUAL in 16 subjects from age 3 to 72, with at least 3 repeated measurements on each subject, each taken for approximately 10 s, at approximately 30 frames per second, with illumination of the ipsilateral eye. PUAL was calculated using the algorithm of the Neurolight pupillometer. We found that average PUAL typically declines by approximately 1% per year, and that the standard deviation of repeated measurements is approximately 20%. We therefore conclude that repeated, averaged measurements of age-normed PUAL are likely to be much more clinically useful than single, uncorrected values.