Blue light (380–500 nm) from LEDs, smartphones, and computers has two distinct biological effects. On the retina, high-energy photons generate free radicals in the photoreceptors through photooxidation—a mechanism implicated in digital eye strain and the progressive degeneration of retinal cells. In the brain, melanopsin-containing ganglion cells (ipRGCs), which are most sensitive at 480 nm, transmit the light signal to the central circadian clock. Evening exposure suppresses melatonin and shifts its peak by 1 to 2 hours, delaying the onset of sleep and reducing deep sleep.
A circadian hormone as well as a powerful retinal antioxidant, melatonin is synthesized in the photoreceptors and the retinal pigment epithelium, where it activates SOD, catalase, and glutathione peroxidase to neutralize nocturnal free radicals. Its nocturnal retinal production protects photoreceptors from damage accumulated during the day. A supplement of 0.5 to 1 mg taken 30 minutes before bedtime supports this repair mechanism in cases of late-night screen exposure—without replacing the need to reduce exposure itself.
Tryptophan (L-tryptophan) is the dietary precursor to serotonin and, subsequently, to melatonin via the enzyme AANAT. Nighttime blue light inhibits this enzyme, blocking the conversion to melatonin. A supplement of 500 mg to 1 g in the evening increases the availability of the precursor and supports melatonin resynthesis during periods of low light. Griffonia (5-HTP, an intermediate precursor) is a more direct, bioavailable alternative to free tryptophan, particularly effective when combined with magnesium.
Magnesium acts on two levels. On the circadian level, it serves as a cofactor for the enzymes involved in melatonin synthesis (tryptophan hydroxylase, AANAT)—a magnesium deficiency, which is very common, exacerbates screen-related difficulty falling asleep. At the ocular level, it regulates the calcium channels of ipRGCs stimulated by melanopsin and reduces the accommodation spasm of the lens characteristic of digital eye strain. At 300–400 mg/day of bisglycinate or glycerophosphate, its highly bioavailable form outperforms conventional mineral forms for chronically tired eyes.
Three protective measures with varying levels of evidence. Glasses with filtering lenses (420–450 nm) reduce direct retinal exposure—a meta-analysis (Singh et al., 2021) shows a moderate reduction in eye strain but inconclusive effects on sleep compared to overall brightness reduction. Night mode (software filter) reduces blue light emission by 30–50% and has been shown to be effective as a complementary measure. Reducing overall brightness to below 50% in the evening remains the most well-documented measure for suppressing melatonin. The most effective behavioral rule remains turning off screens 1 hour before bedtime.
