Relative light sensitivities of four retinal hemi-fields for suppressing the synthesis of melatonin at night

Mark S Rea; Rohan Nagare; Mariana G Figueiro

doi:10.1016/j.nbscr.2021.100066

Relative light sensitivities of four retinal hemi-fields for suppressing the synthesis of melatonin at night

Neurobiol Sleep Circadian Rhythms. 2021 Apr 18:10:100066. doi: 10.1016/j.nbscr.2021.100066. eCollection 2021 May.

Authors

Mark S Rea¹, Rohan Nagare¹, Mariana G Figueiro¹

Affiliation

¹ Light and Health Research Center, Department of Population Health Science and Policy, Icahn School of Medicine at Mount Sinai, New York, NY, USA.

Abstract

The magnitude of the stimulus to the biological clock will depend upon the distribution of circadian phototransduction circuits across the retinae and the spatial distribution of luminous stimuli in the environment. The present study compared nocturnal melatonin suppression for light exposures to the superior, inferior, nasal, and temporal retina in one eye independent of shading from the brow and the nose. The stimulus was a 40° diameter luminous disc, half of which was blue light (LED, λ_peak = 470 nm) and the other amber light (LED, λ_peak = 590 nm). Experimentally, the orientation of the bipartite disc was rotated to each of the four cardinal points of the visual field. A full, 40° blue disc was also employed by replacing the amber half-disc with another blue half-disc. The blue full- and half-discs always produced 100 photopic lx at the cornea. As hypothesized, nocturnal melatonin suppression was statistically greatest when the blue half-disc was delivered to the nasal hemi-field (35%); the other three hemi-fields were equally affected by the blue half-disc (≈20%). Melatonin suppression for the full-disc was 24%, which was not statistically different than the average suppression for the four hemi-fields of 27%.

Keywords: ANOVA, analysis of variance; Blue light; CLA, circadian light; CS, circadian stimulus; Circadian phototransduction; EML, equivalent melanopic lux; LED, light-emitting diode; Melatonin suppression; Monocular; Nasal retina; RGB, red, green, blue; α-opic, alpha-opic; λpeak, peak wavelength.