Age-related differences in the pupillary light reflex between children and adolescents in response to red and blue evening light

Abstract

Purpose : To examine age-related differences in the pupillary response to night-time blue or red light exposure between children and adolescents.

Methods : In this study, we included 40 healthy participants aged 8-9 years (n = 21) or 15-16years (n = 19). After maintaining a stable sleep schedule for 5 days, participants remained indoors on day 6 wearing dark glasses to limit bright light exposure and variability in light history. Participants then completed an in-lab pupillary light response (PLR) assessment in the 1 h before their habitual bedtime. After a dim-light adaptation (<1 lux), pupil diameter was measured during a 30 s baseline, 10 s light exposure to either red (627 nm) or blue light (459 nm) presented at the same photon flux (3.0x10¹³ photons/cm²/s), and 40 s recovery. Following a 7-min dim-light re-adaptation, the procedure was repeated for the other light condition (counterbalanced). We examined the impact of light color and age group on: (1) phasic constriction: percent pupil constriction 500 ms after light onset, (2) maximum pupil constriction during the light exposure, (3) slope of constriction during the 10 s light exposure, and (4) the post-illumination pupillary response 6 s after light offset (PIPR 6 s).

Results : Within each age group, the maximum pupil constriction was significantly larger during exposure to blue compared with red light (children: blue = 57.9%, red = 55.7%; adolescents: blue = 53.6%, red = 50.9%). The constriction response was also more sustained during the blue light exposure than the red (p < 0.01, η_p² = 0.41). For adolescents, the PIPR 6 s was significantly larger after blue (13.5%) compared with red light (11.4%). Finally, across both light colors, children had a greater phasic constriction (p < 0.01, η_p² = 0.20) and greater maximum constriction (p < 0.01, η_p² = 0.22) than adolescents.

Conclusions : In children and adolescents, blue light, stimulating melanopsin-expressing ganglion cells, elicited a greater and more sustained pupillary response than red light in the hour before habitual bedtime. The overall amplitude of the response was greater in children than adolescents, suggesting a continuous development of the PLR during childhood.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

 

Results by light color and age group for: (A) phasic constriction; (B) maximum constriction; (C) slope of constriction during light exposure; and (D) PIPR 6 s after light offset.