By 2050, more than half of the world's population is projected to be myopic — needing glasses or contacts to see clearly at a distance — according to a series of international vision studies, in a shift driven not by genetics but by the amount of time children now spend indoors and the relative absence of time spent focusing on the horizon during the years when the eye is still forming

The story begins in Taiwan in the early 1980s, where roughly 10 to 15 percent of school-age children were nearsighted. By the year 2000, the figure among older teens had risen to approximately 84 percent. No human population can shift its genetic profile by a factor of seven in less than two decades. Something else was happening to children’s eyes, and a generation of ophthalmologists has spent the intervening 25 years trying to figure out what. The current best understanding, drawn from systematic reviews of more than 145 studies involving over 2 million participants worldwide, is that the prevalence of myopia — the technical term for nearsightedness, in which the eyeball grows slightly too long during childhood and distant objects no longer focus properly on the retina — is rising at a rate that has no parallel in any other documented condition of vision or physical development. By 2050, on the available projections, slightly more than half of the entire human population will be affected.

According to the Brien Holden Vision Institute’s summary of its 2016 paper in Ophthalmology, the projected global myopia rate will rise from approximately 28 percent in 2010 to approximately 52 percent in 2050 — meaning nearly 5 billion myopic people by mid-century, with roughly 1 billion of them at significantly elevated risk of permanent blindness due to high myopia (defined in the Holden paper as -5 diopters or worse), a more severe form of the condition that increases lifetime risk of retinal detachment, glaucoma, macular degeneration, and cataracts. The findings have since been confirmed and extended by multiple subsequent systematic reviews, most recently a 2025 meta-analysis in the British Journal of Ophthalmology covering global prevalence trends in children and adolescents from 1990 to 2050.

What is actually happening inside the eye

Myopia is, fundamentally, a problem of axial length. The human eye works by focusing incoming light onto the retina at the back of the eyeball. If the eyeball is too long relative to the focusing power of the cornea and lens, the focal point falls in front of the retina rather than on it, and distant objects appear blurry. The condition is typically progressive during childhood and adolescence — the eyeball continues to elongate as the child grows, and the degree of myopia worsens — before stabilising sometime in early adulthood. Once the eye has elongated, the change is structural and effectively permanent. Glasses, contact lenses, and laser refractive surgery can compensate for the optical consequences, but the underlying eyeball remains longer than it would have been in an unaffected individual, with the lifelong elevation in retinal disease risk that comes with it.

The biological mechanism connecting environmental factors to eyeball elongation has been substantially worked out over the past two decades. As reported by Scientific American’s review of recent myopia research, exposure to natural daylight stimulates the release of dopamine in the retina, and retinal dopamine inhibits the axial elongation of the developing eye. Children who spend substantial time outdoors during the critical developmental years — roughly ages 6 to 12 — receive sufficient daylight exposure to maintain dopamine release and keep eyeball growth on a normal trajectory. Children who spend most of their waking hours indoors, in artificial lighting that is typically one to two orders of magnitude dimmer than natural daylight, receive insufficient stimulation of retinal dopamine, and the eye grows longer than it would otherwise.

The two-factor model

Per a peer-reviewed PMC review of the global myopia epidemic, the strongest predictors of myopia onset and progression in children are two specific environmental factors operating in tandem. The first is reduced outdoor time, which limits the dopamine-mediated protection against eyeball elongation. The second is increased near-focus work — reading, writing, screen-based learning, and recreational device use — which forces sustained accommodation of the eye at close distances and appears to contribute independently to axial elongation. The two factors are partly correlated (children who spend more time on near work typically spend less time outdoors) but operate through separable biological mechanisms. A 2018 Canadian study found that each additional hour per week of outdoor time reduces a child’s odds of developing myopia by approximately 14 percent. A separate Chinese cohort found that children with little daylight exposure have approximately 5 times the myopia risk of well-exposed peers, rising to 16 times the risk when low daylight exposure is combined with heavy near-work activity.

The genetic contribution to myopia is real but limited. Children with one or two myopic parents do have elevated risk, and several genetic variants associated with eyeball geometry have been identified. But the timescale of the global increase rules out genetics as the primary driver. The human gene pool has not changed in any meaningful way over the past 50 years. The myopia rate has, in many populations, tripled or quadrupled over the same period. The environmental contribution must therefore account for the great majority of the recent shift, with genetics modulating individual susceptibility rather than driving the population-level trend.

What the COVID years showed

The pandemic lockdowns of 2020-2021 functioned, inadvertently, as a large natural experiment in the link between indoor time and myopia development. As documented by a 2026 Optometry Times review of the global myopia trajectory, large-scale Chinese cohort studies during the lockdown period reported mean myopic shifts of up to -0.30 diopters within just a few months of confinement — substantially faster progression than the same children would have experienced under normal conditions. The effect was most pronounced in children aged 6 to 8, the age window during which the developing eye appears to be most sensitive to environmental input. The lockdown data essentially closed the remaining scientific debate about whether outdoor time and near work were causally related to myopia or merely correlated. The natural experiment produced exactly the prediction that the environmental hypothesis had been making for years.

What can be done

The interventions that have shown the most consistent effects in randomised trials and population-level programmes are also the simplest. Taiwan, which had the world’s most acute childhood myopia epidemic in the late 20th century, has since 2010 mandated that primary-school students spend at least two hours per day outdoors, with measurable effects on school-age myopia rates. Singapore has implemented similar programmes. Several jurisdictions are now prescribing low-dose atropine eye drops to children showing early myopic progression, which has been shown to slow axial elongation by approximately 50 percent over multi-year follow-up. Orthokeratology contact lenses and specialised multifocal lenses can also slow progression. The most effective single intervention, by every available measure, remains the simplest: getting children outdoors, in natural daylight, for at least an hour or two per day, during the years when their eyes are still forming. The biological logic is straightforward. The cultural logic — getting children to put down screens and spend time outside — has, in most modern environments, turned out to be substantially harder than the biology suggested it should be.