A tablet that shifts the clock

When my parents bought our first color television in the early 1970s, they measured off 6 ft from the screen and insisted that we not watch from any closer distance. They feared blinding radiation emanating from the color cathode tube (indeed, in 1967 General Electric did recall 90,000 televisions that produced X-rays at thousands of times the recommended exposure level, but other than with this model, there was no demonstrable risk). Fast forward 40 y, and I see my teenage child spending most free moments in the evenings staring at her computer screen, phone, or tablet at close range. Is there risk in this? In PNAS, Chang et al. (1) provide compelling data that there may indeed be unappreciated effects and perhaps dangers of evening exposure to electronic screens, specifically demonstrating a negative effect on sleep in young adults following evenings spent reading from a tablet-based eReader.

Photons of visible light are ligands for multiple receptors with powerful effects on physiology. Rhodopsin is a canonical G protein-coupled receptor with amplification mechanisms in mammalian rods that allow for cell-level detection of single photons (2). The three cone opsin photopigments, with their remarkable spectral tuning of responses to different photon wavelengths, produce our rich perceptions of color (3). One of the most interesting developments in vision science in the last 20 y has been the discovery of a small population of several thousand intrinsically photosensitive retinal ganglion cells (ipRGCs) in the inner retina that use another opsin family member, melanopsin, for photoreception (4). These cells provide information on light intensity, via a dedicated retinohypothalamic tract, to the suprachiasmatic nuclei (SCNs) of the hypothalamus. The SCNs, in turn, are the brain …

↵¹Email: russvg{at}uw.edu.