Biology subjects

Lazar, R.

Publications and source records attributed to Lazar, R..

6 recordsLinked to original sources

bioRxiv2025

Joint infrared pupil images and near-corneal-plane spectral light exposure data under natural conditions across the adult lifespan

Factors influencing pupil size can be experimentally controlled or held constant in laboratory experiments, but how the pupil reflects changes in retinal input from the visual environment in real-world viewing conditions has yet to be captured in a large, age-diverse sample. In this dataset, we address this research gap by collecting data in a hybrid field-laboratory experiment (N=83, 43 female, age range 18–87 years) using a custom-built, wearable, video-based eye tracker with a spectroradiometer measuring spectral irradiance in the approximate corneal plane, resulting in a total of valid 29,664 recorded spectral irradiance and eye image pairs along with 83 approximately 3-minute-long calibration videos. After an initial 3-minute calibration procedure, 10-minute dark-adaptation period and a 14-minute controlled laboratory light condition, participants moved in and between indoor and outdoor environments of varying spectral irradiance for ∼25–35 minutes and performed a range of everyday tasks. This dataset may provide a basis for developing algorithms for pupil detection, processing, and prediction under natural conditions.

neuroscience↗

bioRxiv2024

Lack of evidence for the contribution of cone photoreceptors to human melatonin suppression and alerting response to light at night

Light exposure at night can suppress melatonin production and increase alertness, primarily through the action of melanopsin-containing intrinsically photosensitive retinal ganglion cells (ipRGCs). This study investigated whether cone photoreceptors also influence melatonin suppression and subjective alertness using non-visual metameric light emitted from a display. Forty-eight participants with normal trichromatic vision were exposed to three lighting conditions: a baseline (9 lxmEDI), constant background (149 lxmEDI), and cone-modulated flickering light targeting different cone combinations and post-receptoral channels (149 lxmEDI) for 2 hours after their habitual bedtime. Salivary melatonin levels and subjective alertness were measured throughout a 9-h protocol. Bayesian analysis showed that cone-modulated flickering light did not significantly affect melatonin suppression or alertness, providing evidence against the hypothesis that cone photoreceptors contribute to these non-visual effects of light. In conclusion, our results suggest cone photoreceptors do not play a measurable role in lights effects on melatonin suppression and subjective alertness at night.

physiology↗

bioRxiv2024

Afternoon to early evening bright light exposure reduces later melatonin production in adolescents

Whether light exposure during the day reduces non-visual light effects later in the evening has not been studied in adolescents. We investigate whether afternoon-early evening (AEE) light interventions (130 lx, 2500 lx, 4.5 hours, compared to 6.5 lx) would increase melatonin levels during later evening light exposure (130 lx) in a counterbalanced crossover study with 22 adolescents (14-17 years, 11 female). Contrary to our hypothesis, evening melatonin levels decreased after AEE bright light exposure, while sleepiness and vigilance were unaffected, and skin temperature showed no clear changes. The AEE light had acute alerting effects and bright light exposure in the 32 hours before laboratory entry was associated with higher evening melatonin and sleepiness. These findings suggest that bright AEE light increases alertness but may delay melatonin production by interfering with circadian rhythms. The study highlights the complex effects of light timing and its implications for managing adolescents light exposure.

neuroscience↗

bioRxiv2023

Regulation of pupil size in natural vision across the human lifespan

Vision is mediated by light passing through the aperture of the eye, the pupil, which changes in diameter from ~2 to ~8 mm from the brightest to the darkest illumination. In addition, with age, mean pupil size declines. In laboratory experiments, factors affecting pupil size can be experimentally controlled or held constant, but how the pupil reflects changes in retinal input from the visual environment under natural viewing conditions is not clear. Here, we address this question in a field experiment (N=83, 43 female, age: 18-87 years) using a custom-made wearable video-based eye tracker with a spectroradiometer measuring spectral irradiance in the approximate corneal plane. Participants moved in and between indoor and outdoor environments varying in spectrum and engaged in a range of everyday tasks. Our real-world data confirm that light-adapted pupil size is determined by light intensity, with clear superiority of melanopic over photopic units, and that it decreases with increasing age, yielding steeper slopes at lower light levels. We find no indication that sex, iris colour or reported caffeine consumption affect pupil size. Taken together, the data provide strong evidence for considering age in personalised lighting solutions and for using melanopsin-weighted light measures to assess real-world lighting conditions.

neuroscience↗

bioRxiv2019

No evidence for an S cone contribution to the human circadian response to light

Exposure to even moderately bright, short-wavelength light in the evening can strongly suppress the production of melatonin and can delay our circadian rhythm. These effects are mediated by the retinohypothalamic pathway, connecting a subset of retinal ganglion cells to the circadian pacemaker in the suprachiasmatic nucleus (SCN) in the brain. These retinal ganglion cells directly express the photosensitive protein melanopsin, rendering them intrinsically photosensitive (ipRGCs). But ipRGCs also receive input from the classical photoreceptors -- the cones and rods. Here, we examined whether the short-wavelength-sensitive (S) cones contribute to circadian photoreception by using lights which differed exclusively in the amount of S cone excitation by almost two orders of magnitude (ratio 1:83), but not in the excitation of long-wavelength-sensitive (L) and medium-wavelength-sensitive (M) cones, rods, and melanopsin. We find no evidence for a role of S cones in the acute alerting and melatonin supressing response to evening light exposure, pointing to an exclusive role of melanopsin in driving circadian responses.

neuroscience↗

bioRxiv2019

Visual and non-visual properties of filters manipulating short-wavelength light

Optical filters and tints manipulating short-wavelength light (so-called \"blue-blocking\" or \"blue-attenuating\") are used as a remedy for a range of ocular, retinal, neurological and psychiatric disorders. In many cases, the only available quantification of the optical effects of a given optical filter is the spectral transmittance, which specifies the amount of light transmitted as a function of wavelength. Here, we propose a novel physiologically relevant and retinally referenced framework for quantifying the visual and non-visual effects of these filters, incorporating the attenuation of luminance (luminance factor), the attenuation of melanopsin activation (melanopsin factor), the shift in colour, and the reduction of the colour gamut (gamut factor). We examined a novel data base of optical transmittance filters (n=120) which were digitally extracted from a variety of sources and find a large diversity in the alteration of visual and non-visual properties. We suggest that future studies and examinations of the physiological effects of optical filters quantify the visual and non-visual effects of the filters beyond the spectral transmittance, which will eventually aid in developing a mechanistic understanding of how different filters affect physiology.

neuroscience↗