Evening Light-Emitting Diode Screen Exposure, Melanopsin-Mediated Circadian Disruption, and Optical Filtration for Sleep Hygiene: A Narrative Review in the Indian Context
Abstract
Sleep complaints are common in India, where recent meta-analytic estimates place the prevalence of insomnia among the highest reported anywhere. Over the same period, digital screen use has risen steeply, with very high daily smartphone use. Light-emitting diode (LED) screens are rich in short-wavelength ("blue") light. That part of the spectrum drives the intrinsically photosensitive retinal ganglion cells (ipRGCs) that set the circadian clock. Evening screen use can therefore blunt melatonin and push circadian timing later. Screen use is not, however, the same as the melanopic light dose actually reaching the retina. Associations between screen time and poor sleep may also reflect a later bedtime, mental and emotional arousal, notifications, and the type of content viewed. A lens would not change any of these. In this narrative review, we trace the melanopsin-ipRGC-suprachiasmatic nucleus pathway, ask how closely LED emission overlaps circadian photoreception, and weigh the evidence for spectacle-lens filtration as an adjunct to sleep hygiene, with a specific eye on India. Standard blue-light-filtering (BLF) lenses and longer-wavelength ("amber"/"orange") wavelength-selective lenses are held to the same evidentiary standard throughout. Systematic-review evidence rates the case that BLF lenses improve sleep as of low certainty, with findings that are indeterminate and heterogeneous rather than clearly negative. Trials of longer-wavelength lenses are small, clinically mixed,…
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