Does Pupil Constriction under Blue and Green Monochromatic Light Exposure Change with Age?

Abstract

Many nonvisual functions are regulated by light through a photoreceptive system involving melanopsin-expressing retinal ganglion cells that are maximally sensitive to blue light. Several studies have suggested that the ability of light to modulate circadian entrainment and to induce acute effects on melatonin secretion, subjective alertness, and gene expression decreases during aging, particularly for blue light. This could contribute to the documented changes in sleep and circadian regulatory processes with aging. However, age-related modification in the impact of light on steady-state pupil constriction, which regulates the amount of light reaching the retina, is not demonstrated. We measured pupil size in 16 young (22.8 ± 4 years) and 14 older (61 ± 4.4 years) healthy subjects during 45-second exposures to blue (480 nm) and green (550 nm) monochromatic lights at low (7 × 1012 photons/cm2/s), medium (3 × 1013 photons/cm2/s), and high (1014 photons/cm2/s) irradiance levels. Results showed that young subjects had consistently larger pupils than older subjects for dark adaptation and during all light exposures. Steady-state pupil constriction was greater under blue than green light exposure in both age groups and increased with increasing irradiance. Surprisingly, when expressed in relation to baseline pupil size, no significant age-related differences were observed in pupil constriction. The observed reduction in pupil size in older individuals, both in darkness and during light exposure, may reduce retinal illumination and consequently affect nonvisual responses to light. The absence of a significant difference between age groups for relative steady-state pupil constriction suggests that other factors such as tonic, sympathetic control of pupil dilation, rather than light sensitivity per se, account for the observed age difference in pupil size regulation. Compared to other nonvisual functions, the light sensitivity of steady-state pupil constriction appears to remain relatively intact and is not profoundly altered by age.

Melatonin suppression and sleepiness in children exposed to blue‐enriched white LED lighting at night

“…This indicates the possibility that the contribution of mRGC to nocturnal melatonin suppression was promoted by high transmittance of the crystalline lens in children, particularly for a short wavelength light (Boettner and Wolter 1962; Barker et al 1991). Nonetheless, in terms of the effects of age-related ocular alteration on physiological functions, there is still a lack of agreement among previous studies (Herljevic et al 2005;Daneault et al 2012;Higuchi et al 2014;Najjar et al 2014;Gimenez et al 2016). According to a recent report, pre-to mid-pubertal children showed significantly greater melatonin suppression than that in children in the late to post-pubertal group (Crowley et al 2015) although there might be no large difference in lens transmittance or pupil size between the two groups (Barker et al 1991;Winn et al 1994), indicating factors other than ophthalmologic characteristics might be involved in the higher sensitivity to evening light in pre-to mid-pubertal children.…”

Melanopsin and Rod–Cone Photoreceptors Play Different Roles in Mediating Pupillary Light Responses during Exposure to Continuous Light in Humans

“…To account for age-dependent differences, we normalized PLR responses to dark-adapted pupil size, i.e. we determined percentage pupillary constriction, which is stable across age groups (Birren et al, 1950; Daneault et al, 2012). In doing so, we found that the sensitivity of pupillary responses in the blind individual was similar to mice without rod-cone function (Lucas et al, 2003; Do et al, 2009) and macaques with pharmacologic blockade of synaptic input to ipRGCs (Gamlin et al, 2007); hence we consider it unlikely that age-related decline in sympathetic or retinal function contributed substantially to differences we observed in pupillary responses between sighted individuals and the older blind patient.…”

Aging and Circadian Rhythms

“…Daneault and colleagues tested whether this impacts response to monochromatic light exposure. They found that while older adults had smaller pupils at dark-adapted baseline and at all light levels tested, the reduction in pupil size in response to light was not different between young and older subjects [136]. Thus, available evidence suggests that light transmission through the lens is altered with age, specifically reducing transmission of short wavelength light.…”