Blue light glasses and night mode: do they work?

Blue-light glasses

Cochrane reviews pool the best trials on a question. This one, published in 2023, found 17 randomised trials of blue-light filtering lenses, with 5 to 156 people each and follow-up from under a day to five weeks.

• Eye strain: there may be no difference from ordinary lenses with computer use in the short term (low-certainty evidence).
• Sharpness of vision: probably little or no difference.
• Sleep: unclear; the trials reported mixed results in very different groups of people.
• Eye health: no trial measured the health of the retina’s centre, the macula.

Many of the trials were small, and in most the people assessing the results knew who wore which lenses. The reviewers call for better trials. Until then, there is little evidence that the glasses do what they are sold for.

Night mode

Phones can shift their screens to warmer colours in the evening. A trial at a university randomly assigned 167 people aged 18 to 24 to a week of iPhone use in the hour before bed with Night Shift on, with it off, or no phone at all, and measured their sleep with wrist sensors. Across the whole group, sleep did not differ between the three. Among those who usually slept more than 6.8 hours, no phone at all gave the best sleep; Night Shift did not help.

Light still matters

None of this means evening screens are harmless. In a sleep-lab study, reading on a light-emitting e-reader before bed, compared with a printed book, meant falling asleep later, less melatonin and a groggier next morning. Filters change the colour; they do not remove the screen, or what is on it. More in your phone before bed.

What helps more

• For your eyes: regular breaks from close work, a comfortable distance, and an eye doctor if symptoms persist: digital eye strain.
• For your sleep: a fixed time when the phone goes on its charger, outside the bedroom: an evening without your phone.

Nothing to read in bed

Lychnos Ring shows a line or two at a time; there is nothing on it to read in bed for an hour. It is in development and makes no health claims.

Sources, read 4 November 2026: Singh and colleagues, blue-light filtering spectacle lenses for visual performance, sleep, and macular health in adults, Cochrane Database of Systematic Reviews, 2023; Duraccio and colleagues, does iPhone Night Shift mitigate negative effects of smartphone use on sleep outcomes in emerging adults?, Sleep Health, 2021; Chang, Aeschbach, Duffy and Czeisler, evening use of light-emitting eReaders, PNAS, 2015. Abstracts read at Europe PMC. General information, not medical advice.