Most phones and tablets have a "night mode" or "warm display" setting designed to reduce blue light in the evening. The idea is to help your body wind down before sleep. But if your toddler uses a screen at any time of day, there's a reasonable case for keeping that filter on all the time.
Why toddlers are more affected by screen light
Young children's eyes are structurally different from adults'. Toddlers have larger pupils and more transparent lenses, which means more light (especially short-wavelength blue light) reaches the back of their eyes (LeBourgeois, 2017).
A 2018 study from the University of Colorado Boulder measured how preschool-age children's bodies respond to bright light in the hour before bedtime. The children's melatonin levels were reduced by around 88%, a much larger response than is typically seen in adults (Akacem, 2018). Melatonin is the hormone that signals to the body that it is time to sleep, and even daytime changes can affect mood and alertness.
What night mode does
Night mode (also called "Night Shift" on iPhone, "Night Light" on Android, or "Night light" on Windows) shifts the screen's colour temperature warmer. It reduces blue-wavelength output and replaces it with softer amber and orange tones. It also typically reduces overall brightness slightly.
It is worth being honest: the specific evidence on blue-light-filtering glasses and screen overlays is mixed. A randomised trial in adults found no significant improvement in sleep from blue-light-blocking lenses alone (Singh, 2023). But reducing overall screen brightness and shifting to warmer tones does appear to help, because the key variable is total light intensity reaching the eyes, not just the blue portion in isolation (Royal College of Paediatrics and Child Health, 2019).
The ten-second change
On any device your toddler uses, turn on the warm display filter and leave it on permanently, not just in the evening. Then lower the screen brightness to the most comfortable level. On most devices you can find these settings under Display or Screen.
The most effective approach, supported by both the Royal College of Paediatrics and Child Health and the American Academy of Pediatrics, is to avoid screens entirely in the hour before bedtime (Royal College of Paediatrics and Child Health, 2019) (Council on Communications and Media, 2016). And for the screen time that does happen during the day, a warm, dim display is a simple, reasonable adjustment.
How to turn it on
iPhone or iPad: Settings > Display & Brightness > Night Shift. Turn it on and set the schedule to "Sunrise to Sunset" so it stays on all day. Apple's guide.
Android (Pixel, stock Android): Settings > Display > Night Light. Google's guide.
Samsung Galaxy: Settings > Display > Eye comfort shield. Samsung's guide.
Amazon Fire tablet: Swipe down from the top and tap Blue Shade. Or go to Settings > Display > Blue Shade. Amazon's guide.
Mac: System Settings > Displays > Night Shift. Apple's guide.
Windows: Settings > System > Display > Night light. Microsoft's guide.
Chromebook: Settings > Device > Displays > Night Light. Google's guide.
One thing to try today
Pick up whatever device your child uses most. Go to display settings. Turn on the warm colour filter. Turn the brightness down. It takes ten seconds, and it means screen time from then on is a little gentler on developing eyes.
While you're in your device's settings, it's also worth setting up kid mode. It locks the screen to one app, so edge swipes and stray taps can't exit it.
Sources
- Akacem, L.D., Wright, K.P., & LeBourgeois, M.K. (2018). Sensitivity of the circadian system to evening bright light in preschool-age children. Physiological Reports, 6(5), e13617. https://doi.org/10.14814/phy2.13617
- LeBourgeois, M.K., Hale, L., Chang, A.M., Akacem, L.D., Montgomery-Downs, H.E., & Buxton, O.M. (2017). Digital media and sleep in childhood and adolescence. Pediatrics, 140(Supplement 2), S92-S96. https://doi.org/10.1542/peds.2016-1758J
- Royal College of Paediatrics and Child Health (2019). The health impacts of screen time: a guide for clinicians and parents. RCPCH. https://www.rcpch.ac.uk/resources/health-impacts-screen-time-guide-clinicians-parents
- Council on Communications and Media, American Academy of Pediatrics (2016). Media and Young Minds. Pediatrics, 138(5), e20162591. https://doi.org/10.1542/peds.2016-2591
- Singh, S., Keller, P.R., Busija, L., McMillan, P., Makrai, E., Lawrenson, J.G., & Hull, C.C. (2023). Blue-light filtering spectacle lenses for visual performance, sleep, and macular health in adults. Cochrane Database of Systematic Reviews, Issue 8. https://doi.org/10.1002/14651858.CD013244.pub2