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Differences in the pupillary responses to evening light between children and adolescents
Lauren E Hartstein1, Monique K LeBourgeois2, Mark T Durniak3
1Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO, USA. Lauren.Hartstein@colorado.edu.
Insights
Children exhibit greater sensitivity to evening blue light than adolescents, as indicated by pupillary light responses (PLR). This suggests ongoing development of the non-visual system into adolescence.
Area of Science:
- Ophthalmology
- Neuroscience
- Developmental Biology
Background:
- Intrinsically-photosensitive retinal ganglion cells (ipRGCs) mediate non-visual functions like circadian entrainment and pupillary light response (PLR).
- Non-visual light sensitivity may change during child development.
- PLR is a reliable method to assess non-visual light responses in children.
Purpose of the Study:
- To compare pupillary light responses (PLRs) to blue and red light stimuli in children and adolescents.
- To investigate developmental differences in non-visual photoreception.
Main Methods:
- Forty healthy participants (8-9 years, n=21; 15-16 years, n=19) underwent PLR assessment one hour before bedtime.
- Pupil diameter was measured after adaptation to dim light, followed by exposure to blue or red light and a recovery period.
- Light conditions were counterbalanced across participants.
Main Results:
- Blue light caused significantly greater and more sustained pupil constriction than red light in both age groups.
- Adolescents showed a larger post-illumination pupillary response (PIPR) to blue light compared to red light; this was not observed in children.
- Children exhibited larger phasic and maximal pupil constrictions than adolescents.
Conclusions:
- Blue light elicits a stronger pupillary response than red light, with developmental variations observed.
- Children show a greater rod/cone-driven phasic response compared to adolescents.
- Findings indicate higher sensitivity to evening light in children and continued maturation of the non-visual system through adolescence.
Background:
In the mammalian retina, intrinsically-photosensitive retinal ganglion cells (ipRGC) detect light and integrate signals from rods and cones to drive multiple non-visual functions including circadian entrainment and the pupillary light response (PLR). Non-visual photoreception and consequently non-visual sensitivity to light may change across child development. The PLR represents a quick and reliable method for examining non-visual responses to light in children. The purpose of this study was to assess differences in the PLRs to blue and red stimuli, measured one hour prior to bedtime, between children and adolescents.
Methods:
Forty healthy participants (8-9 years, n = 21; 15-16 years, n = 19) completed a PLR assessment 1 h before their habitual bedtime. After a 1 h dim-light adaptation period (< 1 lx), baseline pupil diameter was measured in darkness for 30 s, followed by a 10 s exposure to 3.0 × 1013 photons/cm2/s of either red (627 nm) or blue (459 nm) light, and a 40 s recovery in darkness to assess pupillary re-dilation. Subsequently, participants underwent 7 min of dim-light re-adaptation followed by an exposure to the other light condition. Lights were counterbalanced across participants.
Results:
Across both age groups, maximum pupil constriction was significantly greater (p < 0.001, ηp2 = 0.48) and more sustained (p < 0.001, ηp2 = 0.41) during exposure to blue compared to red light. For adolescents, the post-illumination pupillary response (PIPR), a hallmark of melanopsin function, was larger after blue compared with red light (p = 0.02, d = 0.60). This difference was not observed in children. Across light exposures, children had larger phasic (p < 0.01, ηp2 = 0.20) and maximal (p < 0.01, ηp2 = 0.22) pupil constrictions compared to adolescents.
Conclusions:
Blue light elicited a greater and more sustained pupillary response than red light in children and adolescents. However, the overall amplitude of the rod/cone-driven phasic response was greater in children than in adolescents. Our findings using the PLR highlight a higher sensitivity to evening light in children compared to adolescents, and continued maturation of the human non-visual photoreception/system throughout development.
