Spectral dependency of the human pupillary light reflex. Influences of pre-adaptation and chronotype

Abstract

Non-visual photoreceptors (ipRGCs) and rods both exert a strong influence on the human pupil, yet pupil models regularly use cone-derived sensitivity as their basis. This inconsistency is further exacerbated by the fact that circadian effects can modulate the wavelength sensitivity. We assessed the pupillary reaction to monochromatic light stimuli in the mesopic range. Pupil size for eighty-three healthy participants with normal color vision was measured in nine experimental protocols with varying series of continuous or discontinuous light stimuli under Ganzfeld conditions, presented after 90 seconds of dark adaptation. One hundred and fifty series of stimulation were conducted across three experiments, and were analyzed for wavelength-dependency on the pupillary constriction amplitude (PCA), conditional on experimental settings and individual traits. Traits were surveyed by questionnaire; color vision was tested by Ishihara plates or the Lanthony D15 test. Data were analyzed with generalized additive mixed models (GAMM). The pupillary constriction amplitude response is consistent with L+M-cone derived sensitivity when the series of light stimuli is continuous, i.e., is not interrupted by periods of darkness, but not otherwise. The results also show that a mesopic illuminance weighing led to an overall best prediction of pupillary constriction compared to other types of illuminance measures. IpRGC influence on PCA is not readily apparent from the results. When we explored the interaction of chronotype and time of day on the wavelength dependency, differences consistent with ipRGC influence became apparent. The models indicate that subjects of differing chronotype show a heightened or lowered sensitivity to short wavelengths, depending on their time of preference. IpRGC influence is also seen in the post-illumination pupil reflex if the prior light-stimulus duration is one second. However, shorter wavelengths than expected become more important if the light-stimulus duration is fifteen or thirty seconds. The influence of sex on PCA was present, but showed no interaction with wavelength. Our results help to define the conditions, under which the different wavelength sensitivities in literature hold up for monochromatic light settings. The chronotype effect might signify a mechanism for strengthening the individual´s chronotype, but demands replication in a controlled study.

Assessment of the changes in cardiac sympathetic nervous activity using the pupil size changes measured in seated patients whose stellate ganglion is blocked by interscalene brachial plexus block

“…In contrast, the measurement of pupil diameter using a pupillometer is more feasible because it requires only 2 seconds (in this study) and is resistant to artifacts [19]. In addition, because pupil size reaches plateau within seconds in a dark condition, its measurements require a few seconds of adaptation [44]. Given that SGB has actions on both the oculosympathetic and cardiac sympathetic pathways, we expected that the changes in the pupil diameter reflect those in cardiac SNA and found a significant linear correlation between them.…”

Caracterização circadiana da excitabilidade cortical motora em humanos

“…Padrão similar foi observado para o DLMO 21 , bem como para o RPL relacionado às iPRGcs. 22 Do ponto de vista comportamental e cognitivo, o cronotipo também se associa com diferentes padrões de atividade motora 16 e cognitiva 23 , com maior performance observada no horário preferencial a depender do cronotipo. Em contrapartida, para determinados desfechos, como controle postural, o cronotipo individual não parece ser relevante 24 .…”