Not on its own. Glasses help children learn, the research says, but only if they wear them. And many don’t.
In short
- About 18 million children aged 5 to 17 worldwide cannot see well because they do not have the glasses they need (2024 estimate).
- In randomised trials in China and the United States, free glasses raised test scores by a small amount, though not in every setting or on every test.
- In Baltimore, the gain for the students who were furthest behind was about three times the average.
- The catch: in a large Chinese trial, only 41% of children given free glasses were wearing them in class by the end of the year.
- What helps: glasses handed out at school, teachers who encourage wearing them, and spare pairs.
I assumed this would be a short story. A child can’t see the board, gets glasses, learns more. Done.
The research does suggest that glasses help. But the more closely I read the studies, the more I kept running into a question I had never thought about: what happens after the glasses are handed out?
How many children need glasses but don’t have them?
The most common cause of poor vision in school-age children is something glasses can fix: a refractive error, such as short-sightedness. A WHO analysis estimated that in 2004 about 12.8 million children aged 5 to 15 could not see well because their refractive error was not corrected, nearly three in four of them in Asia.1 More recent Global Burden of Disease data put the figure at around 18 million children aged 5 to 17.2
A 2024 report by Seva Foundation and the International Agency for the Prevention of Blindness pooled four randomised trials, all from China. It estimated that a child who needs glasses but does not have them learns about half as much in a school year as a classmate who sees well, adding up to around 6.3 million years of schooling lost worldwide each year.2
Those are model estimates, not measurements. The report was not peer-reviewed, and the “half as much” figure assumes that children actually wear the glasses they are given. As it turns out, that is a big assumption.
What does the strongest evidence show?
The strongest evidence comes from randomised trials, in which some schools get a glasses programme and comparable schools do not.
In rural western China, a trial published in the BMJ followed 3,177 children with poor vision in 252 primary schools; only 15% of them wore glasses at the start.3 Children who received free glasses in class scored higher on a maths test at the end of the year than children who only got a prescription. The difference was about a tenth of a standard deviation, a statistical way of comparing groups: a small effect, and smaller than the researchers had hoped for.
An earlier trial in Gansu, one of the same provinces, found similar or somewhat larger gains, mainly for students who were behind, and suggested very high returns for such a cheap intervention.4 That trial had implementation problems, so its results are less certain.5
In the United States, Johns Hopkins researchers ran a randomised trial of Vision for Baltimore, which brought eye exams and free glasses into city schools.6 Among 2,304 students in grades 3 to 7, scores on one reading test rose after a year, and the gains were largest for the students who needed them most.
Glasses helped most the children who were furthest behind
Effect of receiving glasses on reading scores after one year, Baltimore (effect size)
Where glasses helped, the children who were furthest behind tended to gain the most.
Where did glasses not help?
The results are not uniformly positive, and the null results matter as much as the gains.
- In Baltimore, there was no clear effect on maths or on the state exams, and after two years the researchers could no longer detect a clear benefit on reading.6
- In China, later trials found gains in poor rural schools but not in urban schools for migrant children,7 and in a poorer province but not a wealthier one.8
- A Cochrane review rated the evidence on school results as low certainty.9
So what’s the catch?
Many children do not wear the glasses they are given. In the Chinese trial, an unannounced check at the end of the year found only 41% of children given free glasses wearing them in class, compared with 26% in the comparison group, although 68% said they wore them.3 A review of 20 studies found that, on average, only around 40% of children wore the glasses they had been prescribed.10
The Baltimore researchers suggested the same reason for the fading effect: children tend to wear their glasses less over time.6
Giving children glasses is not the same as children wearing them, and that gap decides whether glasses help them learn.
Why don’t children wear them? The research points to three reasons:
- Lost and broken glasses. In a school programme on the Tohono O’odham Nation in Arizona, two-thirds of children were not wearing their glasses at the next yearly check, even though each had been given two pairs. Most had lost or broken them.11
- The belief that glasses harm the eyes. In rural China, students, parents and teachers often thought glasses should be delayed and might make eyesight worse;12 in the BMJ trial, about 4 in 10 children believed this.3 A randomised trial suggests the opposite: children whose glasses were deliberately made weaker became short-sighted slightly faster.13
- Disliking how they look, or being teased. This comes up in studies worldwide, though less often than lost or broken glasses.10
What helps children keep wearing them?
What helps
- Hand out glasses at school. In the Chinese trial, glasses given in class improved test scores; vouchers to collect free glasses elsewhere did not produce a clear improvement.
- Involve teachers. Children whose teachers advised them to get glasses were nearly three times as likely to accept free ones, and a small reward for teachers raised wearing from about a quarter to more than two-thirds.
- Plan for replacements. Glasses get lost and broken often, so a spare pair or easy replacement keeps children wearing them.
- Talk to families. Clear information about what glasses do, and don’t do, takes away a fear that keeps many children from wearing them.
The evidence on teachers comes from a Chinese cohort study14 and a randomised trial.15
What does this mean for children on the move?
We found no randomised trials of glasses and learning among refugee children. But there is practical experience.
On the Thai–Burma border, a programme for refugee and migrant schools showed that teachers could run vision screening for tens of thousands of pupils, although many children they referred turned out not to need glasses. Most children given simple ready-made glasses saw well with them, and about 6 in 10 of those checked in one camp were still wearing them six months later. This is a programme report, not a trial.16
In the Rohingya camps in Cox’s Bazar, Bangladesh, Orbis International and a local hospital screened more than 48,000 refugees over about 13 months in 2018–19, most of them children, and provided glasses free of charge. Most vision loss in the camps was caused by uncorrected refractive error and cataract: problems that can be treated.17
In Malaysia, refugee children cannot attend public schools and learn in community learning centres instead.18 The Thai–Burma experience suggests that a short training for teachers and a box of ready-made glasses could already reach many of these children, as long as someone follows up on whether the glasses are worn.
What we don’t know yet
Only a handful of randomised trials exist, and almost all of them are from China. The gains in test scores are small, did not appear in every setting, and in Baltimore were no longer clear after two years. We found no trials among refugee children, so what we know about them comes from programme reports. And the large global estimates are models built on a few studies, not counts.
What you can do
Or share this piece with a teacher or someone working in child health.
What I take from this
I started out thinking this was a story about glasses. It turned out to be a story about everything around them: a teacher who notices, a family who trusts the prescription, a spare pair when the first one breaks. That is good news, because those are things schools and learning centres can influence. The glasses really are the easy part.
Read further
A picture book about a boy who gets glasses, is teased and stops wearing them. A gentle way to talk with children about exactly this problem.
How researchers test what really works against poverty, from education to health.
How we wrote this
This piece is based on randomised trials in China and the United States, a Cochrane review, a 2024 report by Seva Foundation and IAPB, a review of studies on why children don’t wear glasses, research on the role of teachers, and programme data from refugee settings in Thailand and Bangladesh. Every source is listed below.
What is less certain: only a handful of trials exist, almost all in China. The estimate that children with poor vision learn half as much is a model built on four Chinese trials, not a direct measurement. The data from refugee settings come from programmes, not trials, and say nothing directly about learning.
Spot a mistake? Let us know and we will correct it and note the change here.
Founder of the Swart Foundation and lisanneswart.com. She studied sociology and writes about what research says on children’s health, safety and education.
About images and names. We do not publish photos in which children can be identified without informed consent from them and their guardians, and we never share the locations of learning centres. When we tell individual stories, we may change names to protect people.
Sources18 sources
- Resnikoff et al. (2008). Global magnitude of visual impairment caused by uncorrected refractive errors in 2004. Bulletin of the WHO. ↩
- Seva Foundation and IAPB (2024). Better Education in Sight: technical report. Not peer-reviewed. ↩
- Ma et al. (2014). Effect of providing free glasses on children’s educational outcomes in China. BMJ. ↩
- Glewwe, Park and Zhao (2016). A better vision for development: eyeglasses and academic performance in rural primary schools in China. Journal of Development Economics. ↩
- GiveWell. Review of eyeglasses programmes for schoolchildren. ↩
- Neitzel et al. (2021). Effect of a randomized interventional school-based vision program on academic performance of students in grades 3 to 7. JAMA Ophthalmology. ↩
- Ma et al. (2021). Journal of Development Effectiveness: trial in rural and migrant schools in China. ↩
- Du et al. (2022). IJERPH: trial in two Chinese provinces. ↩
- Evans et al. (2018). Vision screening for correctable visual acuity deficits in school-age children and adolescents. Cochrane. ↩
- Dhirar et al. (2020). BMC Ophthalmology: systematic review of spectacle wear in children. ↩
- Messer et al. (2012). Optometry and Vision Science: spectacle wear on the Tohono O’odham Nation. ↩
- Li et al. (2010). Focus groups show need for more education in rural China. Archives of Ophthalmology, via AAO. ↩
- Chung et al. (2002). Undercorrection of myopia enhances rather than inhibits myopia progression. Vision Research. ↩
- Wang et al. (2018). Cohort study on teachers and acceptance of free glasses, via Stanford REAP. ↩
- Yi et al. (2015). American Journal of Ophthalmology: randomised trial of teacher incentives, via Stanford REAP. ↩
- Vincent et al. (2017). Conference paper: school vision screening on the Thai–Burma border. ↩
- Ahmed et al. (2020). PLOS Medicine: eye care in the Rohingya camps, Cox’s Bazar. ↩
- UNHCR Help Malaysia. Education. ↩
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