2016Ophthalmology
Holden et al.
145 studies, 2.1 million people
Predicted that about 5 billion people, half the world, will be short-sighted by 2050, and 1 billion highly so.
Find on PubMed ↗Research library · Everyday body care
Eyes: protecting your vision for life
Half the world may be short-sighted by 2050, driven by more close-up screen time and less daylight. Your eyes are also a window into your health: AI can read heart risk and biological age from a single photo of your retina.
Good evidence50%of the world expected to be short-sighted by 2050Holden 2016, Ophthalmology
−9 ptsfewer children became short-sighted with 40 extra minutes outdoors at school (30% vs 40%)He 2015, JAMA, 1,903 children
+2%death risk for each year your retina looks older than you are (AI estimate)Zhu 2022, Br J Ophthalmol, 46,969 adults
01
The basics
How eyes focus, and what goes wrong
Light passes through the cornea and lens and is focused on the retina at the back of the eye. In myopia (short-sightedness), the eyeball grows too long, so distant things blur. High myopia raises the risk of retinal detachment and glaucoma later.
Bright daylight triggers the retina to release dopamine, which slows eyeball growth in children. Indoor light is 10–100 times dimmer than outdoors, which helps explain the global rise in myopia.
After 40, the lens stiffens (presbyopia), so reading glasses become common. Later risks include cataract, glaucoma and macular degeneration, many of which have no early symptoms. Untreated vision loss is now listed as a risk factor for dementia.
Why short-sight happens
In myopia the eyeball grows too long, so light focuses in front of the retina and distant things blur. Daylight in childhood helps keep growth in check.
02
How it works
How daylight protects young eyes
1
Daylight enters
Outdoor light is often 10,000+ lux, even in shade.
2
Retina signals
Bright light boosts dopamine in the retina.
3
Growth slows
Dopamine helps keep the eyeball from growing too long.
4
Sharp distance vision
Light focuses right on the retina.
03
Measure it
Eye checks by age
- Children: vision checks at school entry and every 1–2 years, sooner if they squint or sit close to screens.
- Adults: an eye exam every 2 years, yearly from 60 or if you have diabetes, high myopia or a family history of glaucoma.
- Amsler grid: a simple home check for macular degeneration. Wavy or missing lines need a prompt eye exam.
- Urgent signs: sudden flashes, a shower of floaters, a curtain over vision or a painful red eye need same-day care.
Try your number
LowGoodIdeal
0180
Studies in children suggest about 2 hours of daylight a day lowers the chance of becoming short-sighted.
04
What the research says
The key studies
2015JAMA
He et al.
1,903 children in Guangzhou
An extra 40-minute outdoor class each school day cut new myopia over 3 years from 39.5% to 30.4%.
Find on PubMed ↗2018Nature Biomedical Engineering
Poplin et al.
284,335 patients
A deep-learning model predicted age, sex, smoking, blood pressure and heart risk just from retinal photos.
Find on PubMed ↗2022British Journal of Ophthalmology
Zhu et al.
46,969 UK Biobank adults
Each year that the AI-estimated 'retinal age' exceeded real age raised death risk by 2%.
Find on PubMed ↗2013JAMA
AREDS2 Research Group
4,203 adults with macular degeneration
A supplement with lutein and zeaxanthin (replacing beta-carotene) slowed progression of advanced macular degeneration in people already affected.
Find on PubMed ↗2023Cochrane Database Syst Rev
Singh et al. (Cochrane)
17 trials
Blue-light-filtering glasses made no difference to eye strain from screens.
Find on PubMed ↗05
Take action
Protecting your eyes
Daylight for children, regular checks for adults, and a few screen habits for everyone.
- 1
Kids: 2 hours outside
Daily outdoor time, even in shade or cloud, protects against myopia.
- 2
20-20-20 rule
Every 20 minutes of screen work, look 20 feet (6 m) away for 20 seconds.
- 3
Regular eye exams
Many eye diseases are painless until late. Exams catch them early.
- 4
Leafy greens and fish
Spinach, kale, eggs and oily fish supply lutein and omega-3s for the retina.
- 5
UV sunglasses
Look for UV400 or 100% UV protection to lower cataract risk.
- 6
Blink and hydrate
Screens halve blink rate. Blink fully, take breaks and use a humidifier for dry eyes.
06
Myth or fact
Common myths, checked
✕ MythCarrots give you night vision.
✓ FactThat was wartime propaganda. Vitamin A only helps if you're deficient.
✕ MythReading in dim light damages your eyes.
✓ FactIt can cause tiredness but not lasting damage.
✕ MythWearing glasses makes your eyes weaker.
✓ FactGlasses don't change how your eyes develop. Under-correcting myopia doesn't help either.
✕ MythBlue light from screens damages your eyes.
✓ FactThere's no evidence screen light harms the retina. Eye strain comes from focusing and blinking less.
07
Questions
Frequently asked
Can myopia be slowed in children?
Yes: outdoor time, low-dose atropine drops and special glasses or contact lenses can all slow it. Ask an optometrist.
Do I need reading glasses?
If you hold your phone further away to read, that's presbyopia. It usually starts in the 40s.
Does diabetes affect the eyes?
Yes. High blood sugar damages retinal vessels. People with diabetes need a retinal check every year.
08
Sources
References and related topics
- Holden et al. (2016). Ophthalmology. 145 studies, 2.1 million people. PubMed ↗
- He et al. (2015). JAMA. 1,903 children in Guangzhou. PubMed ↗
- Poplin et al. (2018). Nature Biomedical Engineering. 284,335 patients. PubMed ↗
- Zhu et al. (2022). British Journal of Ophthalmology. 46,969 UK Biobank adults. PubMed ↗
- AREDS2 Research Group (2013). JAMA. 4,203 adults with macular degeneration. PubMed ↗
- Singh et al. (Cochrane) (2023). Cochrane Database Syst Rev. 17 trials. PubMed ↗