What is refractive error?

Refractive error means the eye does not focus light precisely on the retina, so the image is blurred. Myopia (short sight) — the eye is too long, distance vision is blurred. Hyperopia (long sight) — the eye is too short; young people can often compensate by focusing effort, at the cost of eye strain and headaches. Astigmatism — the cornea is shaped more like a rugby ball than a football, so there is no single point of focus and images are blurred at all distances. Presbyopia — from around age 40-45 the lens stiffens and near focusing is progressively lost; this is universal and not a disease. All of these are corrected with spectacles, contact lenses or, in suitable cases, refractive surgery. Collectively, uncorrected refractive error is the largest single cause of vision impairment in the world.

Why is childhood myopia increasing so quickly?

Because the environment children grow up in has changed, not because their genes have. Two factors dominate the evidence: greatly increased time spent on intensive near work — including but not limited to screens — and, crucially, greatly reduced time spent outdoors in daylight. Cluster-randomised school trials in East Asia have shown that adding around 40-80 minutes of outdoor time per school day reduces the number of children who become myopic. The likely mechanism is that high outdoor light intensity stimulates retinal dopamine release, which inhibits the axial elongation of the eye that causes myopia. Notably, outdoor time is more effective at preventing myopia from starting than at slowing it once it has begun — which is why it is fundamentally a school-policy and public health intervention.

Does it matter how myopic a child becomes?

Yes, considerably — and this is the point most often missed. Spectacles correct the focus, but they do not change the underlying structural fact that the eye has grown too long. The longer the eye, the higher the lifelong risk of serious, sight-threatening disease: retinal detachment, myopic macular degeneration (a leading cause of irreversible blindness in East Asia), glaucoma, and earlier cataract. These risks rise progressively with axial length and persist for life regardless of whether the child wears glasses, contact lenses or later has laser surgery. That is why slowing myopia progression in childhood — myopia CONTROL — is a genuinely different clinical goal from simply correcting vision, and why every dioptre of progression prevented has lifelong value.

What treatments slow myopia progression?

Several options with good trial evidence, typically slowing axial elongation by roughly half. Low-dose atropine eye drops (0.01-0.05% nightly) — 0.05% is more effective than 0.01% but causes more light sensitivity and near blur; rebound acceleration can occur on stopping, so tapering is used. Defocus-incorporated spectacle lenses (DIMS, HAL and similar lenslet designs) — ordinary-looking spectacles that impose peripheral myopic defocus. Soft multifocal or dual-focus contact lenses (such as MiSight). Orthokeratology — rigid lenses worn overnight that temporarily reshape the cornea, giving spectacle-free daytime vision, but requiring meticulous hygiene because of a real risk of microbial keratitis. Combined approaches (atropine plus optical) are increasingly used. Ordinary single-vision spectacles have no control effect; under-correcting deliberately does not help and may worsen progression.

Why do so many people not have the spectacles they need?

Because the barriers are in delivery rather than in the science. In many settings there is simply no one trained to perform a refraction within reasonable distance — refraction is often the missing link even where an eye clinic exists. Where services exist, cost is a decisive barrier: for a family, the spectacles, the travel and the lost working day together may exceed several days' income. Awareness matters too — blurred near vision after 45 is frequently accepted as an inevitable part of ageing rather than something correctable for a few dollars. Programmes that work therefore combine screening with immediate on-site refraction and free or very low-cost ready-made spectacle dispensing, rather than issuing a prescription and expecting the patient to act on it later.

How does GMJ News cover refractive error and myopia?

GMJ News covers the global burden of uncorrected refractive error, the childhood myopia epidemic and its environmental drivers, high myopia as a lifelong structural disease risk distinct from refractive correction, axial length monitoring, outdoor time evidence from school-based cluster trials, myopia control options (low-dose atropine, defocus spectacle lenses, orthokeratology, multifocal contact lenses), cycloplegic refraction in children, school eye health programme design, ready-made versus custom spectacles, presbyopia and its economic consequences, and refractive surgery counselling. Directly relevant to PHIG's eye health, school health and health systems programmes.

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Refractive Error and Myopia

GMJ News knowledge hub · last reviewed September 2026 · Georgian Medical Journal

Summary Statistics Glossary GMJ news FAQ Documents Organizations Research

Uncorrected refractive error — myopia, hyperopia, astigmatism and presbyopia — is the single largest cause of vision impairment globally, affecting an estimated 157 million people with distance vision impairment and 510 million with near vision impairment, virtually all of it correctable with a pair of spectacles costing a few dollars, making it the starkest example in medicine of an entirely solved clinical problem that remains unsolved as a delivery problem (WHO). Superimposed on this is a genuine epidemiological emergency: myopia prevalence in children has risen dramatically across East and Southeast Asia, exceeding 80-90% in some urban cohorts by the end of secondary schooling, driven by intensive near work and — critically — reduced time outdoors, with high myopia carrying lifelong elevated risks of retinal detachment, myopic maculopathy, glaucoma and cataract; evidence-based control measures now include increased outdoor time, low-dose atropine 0.01-0.05%, orthokeratology and specialised defocus spectacle lenses.

Key messages

The largest single cause of vision impairment globally — and the cheapest to fix

Uncorrected refractive error causes distance vision impairment in an estimated 157 million people and near vision impairment in around 510 million — the largest single contributor to global vision impairment. Virtually all of it is correctable with a pair of spectacles. It is the clearest example in medicine of a fully solved clinical problem that remains an unsolved delivery problem: the barriers are availability of refraction services, cost, distance and awareness, not scientific uncertainty.

The childhood myopia epidemic is real and geographically concentrated

Myopia prevalence among children and young adults has risen dramatically over recent decades, most steeply in East and Southeast Asia, where prevalence in urban cohorts finishing secondary school exceeds 80-90% in several studies, with high myopia (worse than -6.00D) affecting a substantial minority. Prevalence is rising more slowly but measurably in Europe, North America and elsewhere. Global projections suggest around half the world population could be myopic by 2050. This is a change in environment, not genetics — genetics cannot change over two generations.

High myopia is not just a spectacle prescription — it is a lifelong disease risk

The reason the epidemic matters clinically: axial elongation of the globe carries permanent, dose-dependent risks that persist regardless of optical or surgical correction. High myopia substantially increases lifetime risk of: retinal detachment; myopic macular degeneration (a leading cause of irreversible blindness in East Asia); open-angle glaucoma; and earlier cataract. Correcting the refractive error with spectacles, contact lenses or laser surgery corrects the FOCUS but does not reduce these structural risks. This is why myopia CONTROL in childhood — slowing axial elongation — is a fundamentally different goal from myopia correction.

Outdoor time is the best-supported preventive intervention

Time spent outdoors in daylight reduces the incidence of new myopia in children — supported by cluster-randomised school-based trials (notably in Guangzhou and Taiwan) and consistent cohort data. Around two hours per day is the commonly cited target. The mechanism is thought to involve high ambient light intensity stimulating retinal dopamine release, which inhibits axial elongation, rather than simply displacing near work. Importantly, outdoor time appears more effective at PREVENTING myopia onset than at slowing progression once myopia has developed — making it a public health and school-policy intervention as much as a clinical one.

Low-dose atropine, orthokeratology and defocus lenses slow progression

Established myopia control options: low-dose atropine eye drops (0.01% to 0.05% — higher concentrations more effective but with more photophobia, near blur and rebound on cessation; 0.05% currently has the best efficacy-tolerability balance in the ATOM and LAMP studies); orthokeratology (overnight rigid contact lenses reshaping the cornea — effective but carries a real risk of microbial keratitis requiring rigorous hygiene); soft multifocal or peripheral-defocus contact lenses (MiSight); and defocus incorporated spectacle lenses (DIMS, HAL/lenslet designs) which slow axial elongation by around 50-60% in trials. These reduce progression; none stops it.

Presbyopia — 510 million with uncorrected near vision impairment

Presbyopia — the age-related loss of accommodative amplitude from lens stiffening, universally beginning around age 40-45 — is not a disease but its uncorrected form is the single largest cause of near vision impairment worldwide. Its economic consequences are substantial and under-appreciated: loss of near vision removes the ability to do close work (tailoring, weaving, sorting, fine assembly, reading, phone use) precisely in the most economically productive years, and studies of ready-made reading spectacle provision in tea pickers and textile workers have demonstrated measurable productivity and income gains. Simple ready-made reading spectacles resolve most cases at very low cost.

Key statistics

157M / 510M

people with distance / near vision impairment from uncorrected refractive error

WHO World Report on Vision

80-90%+

myopia prevalence in some urban East Asian secondary school-leaver cohorts

Ophthalmology/IMI

~2 hours/day

outdoor time associated with reduced myopia incidence in school-based trials

JAMA/Ophthalmology

0.05% atropine

best efficacy-tolerability balance for myopia control in the LAMP study

LAMP/Ophthalmology

50-60%

reduction in axial elongation with defocus-incorporated spectacle lenses in trials

IMI/BJO

Correction ≠ control

spectacles fix focus but do not reduce the structural risks of high myopia

IMI

Myopia control interventions — approximate reduction in axial elongation

Source: International Myopia Institute. Outdoor time chiefly prevents onset; optical and pharmacological methods slow progression.

Glossary of key terms

Types of refractive error
OpticsMyopia (short sight): the eye is too long relative to its optical power, so light focuses in front of the retina — distance blurred, near clear; corrected with concave (minus) lenses. Hyperopia (long sight): the eye is too short, light focuses behind the retina; young patients compensate by accommodating, which can cause asthenopia (eye strain), headache and — in children — accommodative esotropia; corrected with convex (plus) lenses. Astigmatism: the cornea or lens has different curvatures in different meridians, so there is no single point focus — blur at all distances; corrected with cylindrical lenses. Presbyopia: age-related loss of accommodative amplitude, universal from around 40-45; corrected with reading additions, bifocals or varifocals. Anisometropia: a significant difference in refractive error between the two eyes — an important amblyopia risk in children.

Axial length and myopia progression
OphthalmologyAxial length — the front-to-back dimension of the eye — is the primary structural driver of myopia and now the key metric in myopia control practice, measured non-invasively by optical biometry. Approximately 1mm of axial elongation corresponds to roughly 2.5-3.0 dioptres of myopia. Normal adult axial length is around 23-24mm; axial length above approximately 26mm is associated with markedly increased risk of myopic maculopathy and retinal detachment. Monitoring axial length rather than refraction alone is preferred in children on myopia control because it is not confounded by accommodation or cycloplegia and detects treatment failure earlier. Percentile growth charts for axial length by age and sex are now used in the same way paediatricians use height charts.

Cycloplegic refraction in children
Paediatric optometryChildren have powerful accommodation that can mask hyperopia entirely and can produce a falsely myopic result (pseudomyopia) on non-cycloplegic testing. Cycloplegic refraction — using cyclopentolate 1% (or atropine in accommodative esotropia and in some high-hyperopia assessments) to temporarily paralyse accommodation — is therefore mandatory for accurate refraction in children, and is the standard for epidemiological myopia studies. Failure to cycloplege is one of the commonest sources of error in paediatric prescribing, leading to under-correction of hyperopia (which may be causing esotropia or amblyopia) and over-diagnosis of myopia. It is also essential before prescribing for any child with strabismus.

School eye health programmes
Public healthVision screening in schools followed by refraction and provision of spectacles is one of the most cost-effective health interventions available, with demonstrated effects on educational outcomes — randomised studies of spectacle provision to myopic children in China have shown measurable improvements in test scores. Programme design determines success far more than screening technique: the critical failure points are children who screen positive but never receive refraction; children who receive a prescription but never obtain spectacles because of cost; and children who obtain spectacles but do not wear them due to stigma, poor fit or breakage. Effective programmes therefore combine screening with on-site refraction and immediate free spectacle dispensing, teacher and parent engagement, and replacement provision.

Refractive surgery
OphthalmologyLASIK (flap created, stromal ablation beneath), PRK/LASEK (surface ablation, no flap — preferred in thin corneas and in those at risk of ocular trauma), and SMILE (lenticule extraction through a small incision) reshape the cornea to correct refractive error. Phakic intraocular lenses (ICL) are used for high myopia beyond safe corneal ablation limits. Refractive lens exchange replaces the crystalline lens, and is essentially cataract surgery performed for refractive reasons — carrying the same risks, plus a higher retinal detachment risk in high myopes. Key counselling points: surgery corrects focus but does NOT reduce the retinal and glaucoma risks of high myopia; dry eye is the commonest postoperative complaint; ectasia is the most serious complication (screened for by corneal topography and tomography); and presbyopia will still develop on schedule.

Ready-made vs custom spectacles
Global eye healthReady-made spectacles — pre-manufactured, with the same spherical power in both lenses — cost a fraction of custom spectacles and can be dispensed immediately at the point of screening without a laboratory. Randomised comparisons have shown high acceptability and visual satisfaction for suitable patients. They are appropriate when: astigmatism is low (generally below about 0.75-1.00D); anisometropia is minimal; and no significant ocular pathology is present. They are unsuitable for children with significant astigmatism or anisometropia, or where amblyopia risk exists. Ready-made reading spectacles for presbyopia are the highest-volume, lowest-cost, highest-impact application, and are the core of most large-scale presbyopia correction programmes.

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