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Myopia
Other namesnear-sightedness, short-sightedness
Diagram showing changes in the eye with myopia
SpecialtyOphthalmology, optometry
SymptomsDistant objects appear blurry, headaches, eye strain[1]
ComplicationsRetinal detachment, cataracts, glaucoma[2]
DurationTypically permanent once it develops
CausesCombination of genetic and environmental factors[2]
Risk factorsNear work, greater time spent indoors, family history[2][3]
Diagnostic methodEye examination[1]
PreventionUnknown
TreatmentEyeglasses, contact lenses, surgery[1]
MedicationLow-dose atropine eye drops[4]
PrognosisGenerally stable after it progresses in early adulthood[5]
FrequencyApproximately 30% of people around the world[6]
DeathsNot deadly

Myopia, also known as near-sightedness and short-sightedness,[7] is an eye condition[8][9] where light from distant objects focuses in front of, instead of on, the retina.[1][2][10] As a result, distant objects appear blurry, while close objects appear normal.[1] Other symptoms may include headaches and eye strain.[1][11] Severe myopia is associated with an increased risk of macular degeneration, retinal detachment, cataracts, and glaucoma.[2][12]

Myopia results from the length of the eyeball growing too long or less commonly the lens being too strong.[1][13] It is a type of refractive error.[1] Diagnosis is by the use of cycloplegics during eye examination.[14]

Myopia is less common in people who spent more time outside during childhood.[15][16] This lower risk may be due to greater exposure to sunlight.[17][18] Myopia can be corrected with eyeglasses, contact lenses, or by refractive surgery.[1][19] Eyeglasses are the simplest and safest method of correction.[1] Contact lenses can provide a relatively wider corrected field of vision, but are associated with an increased risk of infection.[1][20] Refractive surgeries such as LASIK and PRK permanently change the shape of the cornea. Other procedures include implantable collamer lens (ICL) placement inside the anterior chamber in front of the natural eye lens. ICL does not affect the cornea.[1][21]

Myopia is the most common eye problem and is estimated to affect 1.5 billion people (22% of the world population).[2][22] Rates vary significantly in different areas of the world.[2] Rates among adults are between 15% and 49%.[3][23] Among children, it affects 1% of rural Nepalese, 4% of South Africans, 12% of people in the US, and 37% in some large Chinese cities.[2][3] In China the proportion of girls is slightly higher than boys.[24] Rates have increased since the 1950s.[23] Uncorrected myopia is one of the most common causes of vision impairment globally along with cataracts, macular degeneration, and vitamin A deficiency.[23][25][26][27]

Signs and symptoms

[edit]
Near-sighted vision vs. normal vision

A person with myopia can see clearly out to a certain distance (the far point of the eye), but objects placed beyond this distance appear blurred.[19][28] If the extent of the myopia is great enough, even standard reading distances can be affected. Upon routine examination of the eyes, the vast majority of myopic eyes appear structurally identical to nonmyopic eyes.[29][28]

Onset is often in school children, with worsening between the ages of 8 and 15.[30][31]

Myopic individuals have larger pupils than far-sighted (hypermetropic) and emmetropic individuals, likely due to requiring less accommodation (which results in pupil constriction).[32][33]

Causes

[edit]

The underlying cause of myopia is believed to be a combination of genetic and environmental factors.[2][34][35] Risk factors include doing work that involves focusing on close objects, greater time spent indoors, urbanization, and a family history of the condition.[2][3][36][37] It is also associated with a high socioeconomic class and higher level of education.[2][37]

A 2012 review could not find strong evidence for any single cause, although many theories have been discredited.[38] Twin studies indicate that at least some genetic factors are involved.[30][39][40] Myopia has been increasing rapidly throughout the developed world, suggesting environmental factors are involved.[41]

The role of corrective lenses interfering with emmetropization has also been suggested.[42][43]

Genetics

[edit]

A risk for myopia may be inherited from one's parents.[44] Genetic linkage studies have identified 18 possible loci on 15 different chromosomes that are associated with myopia, but none of these loci is part of the candidate genes that cause myopia. Instead of a simple one-gene locus controlling the onset of myopia, a complex interaction of many mutated proteins acting in concert may be the cause. Instead of myopia being caused by a defect in a structural protein, defects in the control of these structural proteins might be the actual cause of myopia.[45] A collaboration of all myopia studies worldwide identified 16 new loci for refractive error in individuals of European ancestry, of which 8 were shared with Asians. The new loci include candidate genes with functions in neurotransmission, ion transport, retinoic acid metabolism, extracellular matrix remodeling and eye development. The carriers of the high-risk genes have a tenfold increased risk of myopia.[46] Aberrant genetic recombination and gene splicing in the OPNLW1 and OPNMW1 genes that code for two retinal cone photopigment proteins can produce high myopia by interfering with refractive development of the eye.[47][48]

Human population studies suggest that contribution of genetic factors accounts for 60–90% of variance in refraction.[49][50][51][52] However, the currently identified variants account for only a small fraction of myopia cases, suggesting the existence of a large number of yet unidentified low-frequency or small-effect variants, which underlie the majority of myopia cases.[53]

Environmental factors

[edit]

Environmental factors that increase the risk of myopia include insufficient light exposure, low physical activity, near work, and increased years of education.[30][43]

One hypothesis is that a lack of normal visual stimuli causes improper development of the eyeball. Under this hypothesis, "normal" refers to the environmental stimuli that the eyeball evolved to.[54] Modern humans who spend most of their time indoors, in dimly or fluorescently lit buildings may be at risk of development of myopia.[54]

People, and children especially, who spend more time doing physical exercise and outdoor play, have lower rates of myopia,[55][54][56][57][41] suggesting the increased magnitude and complexity of the visual stimuli encountered during these types of activities decrease myopic progression. There is preliminary evidence that the protective effect of outdoor activities on the development of myopia is due, at least in part, to the effect of long hours of exposure to daylight on the production and the release of retinal dopamine.[41][58][59][60]

Myopia can be induced with minus spherical lenses,[61] and overminus in prescription lenses can induce myopia progression.[62][63] Overminus during refraction can be avoided through various techniques and tests, such as fogging, plus to blur, and the duochrome test.[63]

The near work hypothesis, also referred to as the "use-abuse theory", states that spending time involved in near work strains the intraocular and extraocular muscles. Some studies support the hypothesis, while other studies do not.[3] While an association is present, it is not clearly causal.[3]

Myopia is also more common in children with diabetes, childhood arthritis, uveitis, and systemic lupus erythematosus.[30]

Other factors

[edit]

Research indicates a relationship between body mass index (BMI) and myopia, with both low and high BMI associated with an increased risk of developing myopia. A nationwide study of 1.3 million Israeli adolescents found that individuals with underweight status had higher chances of mild-to-moderate and high myopia compared to those with low-normal BMI.[64]

Similarly, a study involving Korean young adult men reported that those who were of average or shorter height and lean had a higher prevalence of high myopia.[65][66]

Mechanism

[edit]

Because myopia is a refractive error, the physical cause of myopia is comparable to any optical system that is out of focus. Borish and Duke-Elder classified myopia by these physical causes:[67][68]

  • Axial myopia is attributed to an increase in the eye's axial length.[69]
  • Refractive myopia is attributed to the condition of the refractive elements of the eye.[69] Borish further subclassified refractive myopia:[67]
    • Curvature myopia is attributed to excessive, or increased, curvature of one or more of the refractive surfaces of the eye, especially the cornea.[69] In those with Cohen syndrome, myopia appears to result from high corneal and lenticular power.[70]
    • Index myopia is attributed to variation in the index of refraction of one or more of the ocular media.[69]

As with any optical system experiencing a defocus aberration, the effect can be exaggerated or masked by changing the aperture size. In the case of the eye, a large pupil emphasizes refractive error and a small pupil masks it. This phenomenon can cause a condition in which an individual has a greater difficulty seeing in low-illumination areas, even though there are no symptoms in bright light, such as daylight.[71]

Under rare conditions, edema of the ciliary body can cause an anterior displacement of the lens, inducing a myopia shift in refractive error.[72]

Diagnosis

[edit]

A diagnosis of myopia is typically made by an eye care professional, usually an optometrist or ophthalmologist. This is by refracting the eye with the use of cycloplegics such as atropine with responses recorded when accommodation is relaxed.[14] Diagnosis of progressive myopia requires regular eye examination using the same method.[14]

Types

[edit]

Myopia can be classified into two major types; anatomical and clinical. The types of myopia based on anatomical features are axial, curvature, index and displacement of refractive element. Congenital, simple and pathological myopia are the clinical types of myopia.[7]

Various forms of myopia have been described by their clinical appearance:[68][73][74]

  • Simple myopia: Myopia in an otherwise normal eye, typically less than 4.00 to 6.00 diopters.[75] This is the most common form of myopia.
  • Degenerative myopia, also known as malignant, pathological, or progressive myopia, is characterized by marked fundus changes, such as posterior staphyloma, and associated with a high refractive error and subnormal visual acuity after correction.[69] This form of myopia gets progressively worse over time. Degenerative myopia has been reported as one of the main causes of visual impairment.[76]
  • Pseudomyopia is the blurring of distance vision brought about by spasm of the accommodation system.[77]
  • Nocturnal myopia: Without adequate stimulus for accurate accommodation, the accommodation system partially engages, pushing distance objects out of focus.[75]
  • Nearwork-induced transient myopia (NITM): short-term myopic far point shift immediately following a sustained near visual task.[78] Some authors argue for a link between NITM and the development of permanent myopia.[79]
  • Instrument myopia: over-accommodation when looking into an instrument such as a microscope.[74]
  • Induced myopia, also known as acquired myopia, sometimes reversible myopic shift, results from various medications, increases in glucose levels, nuclear sclerosis, oxygen toxicity (e.g., from underwater diving or from oxygen and hyperbaric therapy) or other anomalous conditions.[80][75] Sulphonamide therapy can cause ciliary body edema, resulting in anterior displacement of the lens, pushing the eye out of focus.[72] Elevation of blood-glucose levels can also cause edema (swelling) of the crystalline lens as a result of sorbitol accumulating in the lens. This edema often causes temporary myopia. Scleral buckles, used in the repair of retinal detachments may induce myopia by increasing the axial length of the eye.[81]
  • Index myopia is attributed to variation in the index of refraction of one or more of the ocular media.[69] Cataracts may lead to index myopia.[82]
  • Form deprivation myopia occurs when the eyesight is deprived by limited illumination and vision range,[83] or the eye is modified with artificial lenses[84] or deprived of clear form vision.[85] In lower vertebrates, this kind of myopia seems to be reversible within short periods of time. Myopia is often induced this way in various animal models to study the pathogenesis and mechanism of myopia development.[86]

Degree

[edit]

The degree of myopia is described in terms of the power of the ideal correction, which is measured in diopters:[87]

The highest myopia ever recorded was −108 diopters by a Slovak, Jan Miskovic.[97]

Age at onset

[edit]

Myopia is sometimes classified by the age at onset:[87]

  • Congenital myopia, also known as infantile myopia, is present at birth and persists through infancy.[75]
  • Youth onset myopia occurs in early childhood or teenage, and the ocular power can keep varying until the age of 21, before which any form of corrective surgery is usually not recommended by ophthalmic specialists around the world.[75]
  • School myopia appears during childhood, particularly the school age years.[98] This form of myopia is attributed to the use of the eyes for close work during the school years.[69] A 2004–2015 Singapore–Sydney study of children of Chinese descent found that time spent on outdoor activities was a factor.[99]
  • Adult onset myopia
  • Early adult onset myopia occurs between ages 20 and 40.[75]
  • Late adult onset myopia occurs after age 40.[75]

Prevention and control

[edit]

Various methods have been employed in an attempt to decrease the progression of myopia, although studies show mixed results.[100] Many myopia treatment studies have a number of design drawbacks: small numbers, lack of adequate control group, and failure to mask examiners from knowledge of treatments used. The best approach is to combine multiple prevention and control methods.[101] A test of repeated low-level red-light therapy (LLRL) on myopic Chinese children showed it to be a promising alternative treatment for myopia control in children.[102]

Spending time outdoors

[edit]

Some studies have indicated that having children spend time outdoors reduces the incidence of myopia.[103] A 2017 study investigated the leading causal theory of association between greenspace exposure and spectacles use as a proxy for myopia, finding a 28% reduction in the likelihood of spectacles use per interquartile range increase in time spent in greenspace.[104] In Taiwan, government policies that require schools to send all children outdoors for a minimum amount of time have driven down the prevalence of myopia in children.[103][105]

Glasses and contacts

[edit]

The use of reading glasses when doing close work may improve vision by reducing or eliminating the need to accommodate. Altering the use of eyeglasses between full-time, part-time, and not at all does not appear to alter myopia progression.[106][107] The American Optometric Association's Clinical Practice Guidelines found evidence of effectiveness of bifocal lenses and recommends it as the method for "myopia control".[75] In some studies, bifocal and progressive lenses have not shown differences in altering the progression of myopia compared to placebo.[100][108]

In the United States, the Food and Drug Administration (FDA) has approved myopia control contact lenses such as CooperVision's MiSight and Johnson & Johnson Vision's Acuvue Abiliti. Yet the agency has yet to approve any myopia control spectacle lenses.

Medication

[edit]

Anti-muscarinic topical medications in children under 18 years of age may slow the worsening of myopia.[109][110] These treatments include pirenzepine gel, cyclopentolate eye drops, and atropine eye drops. While these treatments were shown to be effective in slowing the progression of myopia and reducing eyeball elongation associated with the condition, side effects included light sensitivity and near blur.[109][111]

Other methods

[edit]

Scleral reinforcement surgery is aimed to cover the thinning posterior pole with a supportive material to withstand intraocular pressure and prevent further progression of the posterior staphyloma. The strain is reduced, although damage from the pathological process cannot be reversed. By stopping the progression of the disease, vision may be maintained or improved.[112] The use of orthoK can also slow down axial lens elongation.[113]

Treatment

[edit]
Glasses are commonly used to address myopia.

The National Institutes of Health says there is no known way of preventing myopia, and the use of glasses or contact lenses does not affect its progression, unless the glasses or contact lenses are too strong of a prescription.[114] There is no universally accepted method of preventing myopia and proposed methods need additional study to determine their effectiveness.[75] Optical correction using glasses or contact lenses is the most common treatment; other approaches include orthokeratology, and refractive surgery.[75]: 21–26  Medications (mostly atropine) and vision therapy can be effective in addressing the various forms of pseudomyopia.

Compensating for myopia using a corrective lens

Glasses and contacts

[edit]
Prismatic color distortion shown with a camera set for near-sighted focus, and using −9.5 diopter eyeglasses to correct the camera's myopia (left). Close-up of color shifting through corner of eyeglasses. The light and dark borders visible between color swatches do not exist (right).

Corrective lenses bend the light entering the eye in a way that places a focused image accurately onto the retina. The power of any lens system can be expressed in diopters, the reciprocal of its focal length in meters. Corrective lenses for myopia have negative powers because a divergent lens is required to move the far point of focus out to the distance. More severe myopia needs lens powers further from zero (more negative). However, strong eyeglass prescriptions create distortions such as prismatic movement and chromatic aberration. Strongly myopic wearers of contact lenses do not experience these distortions because the lens moves with the cornea, keeping the optic axis in line with the visual axis and because the vertex distance has been reduced to zero.

Surgery

[edit]

Refractive surgery includes procedures which alter the corneal curvature of some structure of the eye or which add additional refractive means inside the eye.

Photorefractive keratectomy

[edit]
See also: Photorefractive keratectomy

Photorefractive keratectomy (PRK) involves ablation of corneal tissue from the corneal surface using an excimer laser. The amount of tissue ablation corresponds to the amount of myopia. While PRK is a relatively safe procedure for up to 6 dioptres of myopia, the recovery phase post-surgery is usually painful.[115][116]

LASIK

[edit]

In a LASIK pre-procedure, a corneal flap is cut into the cornea and lifted to allow the excimer laser beam access to the exposed corneal tissue. After that, the excimer laser ablates the tissue according to the required correction. When the flap again covers the cornea, the change in curvature generated by the laser ablation proceeds to the corneal surface. Though LASIK is usually painless and involves a short rehabilitation period post-surgery, it can potentially result in flap complications and loss of corneal stability (post-LASIK keratectasia).[117][118]

Phakic intra-ocular lens

[edit]

Instead of modifying the corneal surface, as in laser vision correction (LVC), this procedure involves implanting an additional lens inside the eye (i.e., in addition to the already existing natural lens). While it usually results in good control of the refractive change, it can induce potential serious long-term complications such as glaucoma, cataract and endothelial decompensation.[119][120][121]

Orthokeratology

[edit]
Main article: Orthokeratology

Orthokeratology or simply Ortho-K is a temporary corneal reshaping process using rigid gas permeable (RGP) contact lenses.[122] Overnight wearing of specially designed contact lenses will temporarily reshape cornea, so patients may see clearly without any lenses in daytime. Orthokeratology can correct myopia up to −6D.[123] Several studies shown that Ortho-K can reduce myopia progression also.[124][125] Risk factors of using Ortho-K lenses include microbial keratitis,[124] corneal edema,[126] etc. Other contact lens related complications such as corneal aberration, photophobia, pain, irritation, redness etc. are usually temporary conditions, which may be eliminated by proper usage of lenses.[126]

Intrastromal corneal ring segment

[edit]

The Intrastromal corneal ring segment (ICRS), commonly used in keratoconus treatment now, was originally designed to correct mild to moderate myopia.[127] The thickness is directly related to flattening and the diameter of the ring is proportionally inverse to the flattening of cornea. So, if diameter is smaller or thickness is greater, resulting myopia correction will be greater.[128]

Alternative medicine

[edit]

A number of alternative therapies have been claimed to improve myopia, including vision therapy, "behavioural optometry", various eye exercises and relaxation techniques, and the Bates method.[129] Scientific reviews have concluded that there was "no clear scientific evidence" that eye exercises are effective in treating myopia[130] and as such they "cannot be advocated".[131]

Epidemiology

[edit]

Global refractive errors have been estimated to affect 800 million to 2.3 billion.[132] The incidence of myopia within sampled population often varies with age, country, sex, race, ethnicity, occupation, environment, and other factors.[133][134] Variability in testing and data collection methods makes comparisons of prevalence and progression difficult.[135]

The prevalence of myopia has been reported as high as 70–90% in some Asian countries, 30–40% in Europe and the United States, and 10–20% in Africa.[134] Myopia is about twice as common in Jewish people than in people of non-Jewish ethnicity.[136] Myopia is less common in African people and associated diaspora.[133] In Americans between the ages of 12 and 54, myopia has been found to affect African Americans less than Caucasians.[137]

A 2024 study published in the British Journal of Ophthalmology revealed that more than one-third of children worldwide were nearsighted in 2023, with this figure projected to rise to nearly 40% by 2050.[138] The prevalence of myopia among children and adolescents has increased significantly over the past 30 years, rising from 24% in 1990 to almost 36% in 2023, with researchers noting a sharp spike in cases following the COVID-19 pandemic and highlighting regional differences in myopia rates.[139]

A 2025 South Korean analysis of 45 studies, involving 335,524 participants and largely based on data from children, adolescents and young adults, that looked at the use of digital screen devices such as mobile phones, game consoles and television, revealed that an additional hour of daily screen time is, on average, associated with 21% higher odds of having myopia.[140]

Asia

[edit]
Estimated myopia rate in 20-year-olds in Asia[141]

In some parts of Asia, myopia is very common.

  • Singapore is believed to have the highest prevalence of myopia in the world; up to 80% of people there have myopia, but the accurate figure is unknown.[142]
  • China's myopia rate is 31%: 400 million of its 1.3 billion people are myopic. The prevalence of myopia in high school in China is 77%, and in college is more than 80%.[143]
  • In some areas, such as China and Malaysia, up to 41% of the adult population is myopic to 1.00 dpt,[144] and up to 80% to 0.5 dpt.[145]
  • A study of Jordanian adults aged 17 to 40 found more than half (54%) were myopic.[146]
  • A study indicated that the prevalence of myopia among urban children in India of aged 5 to 15 increased from 4.44% in 1999 to 21.15% in 2019. Projections suggest that by 2050, this figure could reach 48.14%.[147]
  • Some research suggests the prevalence of myopia in Indian children is less than 15%.[148]
  • In South Korea among the general population, national data indicates that 70.6% of the adult population has myopia, with 8.0% affected by high myopia. The prevalence decreases with age, from 81.3% in individuals aged 19 to 24 years to 55.2% in those aged 45 to 49 years.[149]
  • Up to 90% of young people in Taiwan have myopia.[150]

Europe

[edit]
Myopia rate in Europe by birth decade (1910 to 1970)[151]
  • In first-year undergraduate students in the United Kingdom 50% of British whites and 53% of British Asians were myopic.[152]
  • A recent review found 27% of Western Europeans aged 40 or older have at least −1.00 diopters of myopia and 5% have at least −5.00 diopters.[153]

North America

[edit]

Myopia is common in the United States, with research suggesting this condition has increased dramatically in recent decades. In 1971–1972, the National Health and Nutrition Examination Survey provided the earliest nationally representative estimates for myopia prevalence in the U.S., and found the prevalence in persons aged 12–54 was 25%. Using the same method, in 1999–2004, myopia prevalence was estimated to have climbed to 42%.[154]

A study of 2,523 children in grades 1 to 8 (age, 5–17 years) found nearly one in 10 (9%) have at least −0.75 diopters of myopia.[155] In this study, 13% had at least +1.25 D hyperopia (farsightedness), and 28% had at least 1.00-D difference between the two principal meridians (cycloplegic autorefraction) of astigmatism. For myopia, Asians had the highest prevalence (19%), followed by Hispanics (13%). Caucasian children had the lowest prevalence of myopia (4%), which was not significantly different from African Americans (7%).[155]

A recent review found 25% of Americans aged 40 or older have at least −1.00 diopters of myopia and 5% have at least −5.00 diopters.[153]

Australia

[edit]

In Australia, the overall prevalence of myopia (worse than −0.50 diopters) has been estimated to be 17%.[156] In one recent study, less than one in 10 (8%) Australian children between the ages of four and 12 were found to have myopia greater than −0.50 diopters.[157] A recent review found 16% of Australians aged 40 or older have at least −1.00 diopters of myopia and 3% have at least −5.00 diopters.[153]

South America

[edit]

In Brazil, a 2005 study estimated 6% of Brazilians between the ages of 12 and 59 had −1.00 diopter of myopia or more, compared with 3% of the indigenous people in northwestern Brazil.[158] Another found nearly 1 in 8 (13%) of the students in the city of Natal were myopic.[159]

History

[edit]

The difference between the near-sighted and far-sighted people was noted already by Aristotle.[160] Graeco-Roman physician Galen first used the term "myopia" (from Greek words "myein" meaning "to close or shut" and "ops" (gen. opos) meaning "eye") for near-sightedness.[160] The first spectacles for correcting myopia were invented by a German cardinal in the year 1451.[161] Johannes Kepler in his Clarification of Ophthalmic Dioptrics (1604) first demonstrated that myopia was due to the incident light focusing in front of the retina. Kepler also showed that myopia could be corrected by concave lenses.[160] In 1632, Vopiscus Fortunatus Plempius examined a myopic eye and confirmed that myopia was due to a lengthening of its axial diameter.[162]

The idea that myopia was caused by the eye strain involved in reading or doing other work close to the eyes was a consistent theme for several centuries.[105] In Taiwan, faced with a staggering rise in the number of young military recruits needing glasses, the schools were told to give students' eyes a 10-minute break after every half-hour of reading; however, the rate of myopia continued to climb.[105][163] The policy that reversed the epidemic of myopia was the government ordering all schools to have the children outside for a minimum of 80 minutes every day.[163]

Society and culture

[edit]

The terms "myopia" and "myopic" (or the common terms "short-sightedness" or "short-sighted", respectively) have been used metaphorically to refer to cognitive thinking and decision making that is narrow in scope or lacking in foresight or in concern for wider interests or for longer-term consequences.[164] It is often used to describe a decision that may be beneficial in the present, but detrimental in the future, or a viewpoint that fails to consider anything outside a very narrow and limited range. Hyperopia, the biological opposite of myopia, may also be used metaphorically for a value system or motivation that exhibits "farsighted" or possibly visionary thinking and behavior; that is, emphasizing long-term interests at the apparent expense of near-term benefit.[165]

Keeping children indoors, whether to promote early academic activities, because urban development choices leave no place for children to play outside, or because people avoid sunlight because of a preference for lighter skin color, causes myopia.[105] Taiwan has developed an aggressive program to identify pre-school-age children with pre-myopia and treat them with atropine, and to have schools send students outdoors every day.[105] The Tian-tian 120 program ("Every day 120") encourages 120 minutes of outdoor time each day.[105] Compared to the cost of lifelong treatment for myopia with glasses, and in some cases, preventable blindness, the US$13 spent on screening young children for pre-myopia is considered a good investment in public health.[105]

Because myopia can be mitigated through lifestyle choices, it is possible that being myopic will become a marker of an impoverished or neglected childhood, with wealthy families ensuring that their children spend enough time outdoors to prevent or at least reduce it, and poor families, who rely on lower-quality childcare arrangements or not having access to a safe outdoor space, being unable to provide the same benefits to their children.[105]

Correlations

[edit]

Numerous studies have found correlations between myopia, on the one hand, and intelligence and academic achievement, on the other;[166] it is not clear whether there is a causal relationship.[167] Myopia is also correlated with increased microsaccade amplitude, suggesting that blurred vision from myopia might cause instability in fixational eye movements.[168][169]

Etymology

[edit]

The term myopia is of Koine Greek origin: μυωπία myōpia 'short-sight' and μυωπίασις (myōpiasis) 'short-sight-ness'. It is derived from the ancient Greek μύωψ (myōps) 'short-sighted' (man), from μύειν (myein) 'to shut the eyes' and ὤψ (ōps) 'eye, look, sight' (GEN ὠπός (ōpos)).[170][171][172][173][174] The opposite of myopia in English is hypermetropia, or far-sightedness.[175]

See also

[edit]

References

[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Myopia

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from Grokipedia
Myopia, commonly known as nearsightedness, is a refractive error characterized by the inability to see distant objects clearly while near vision remains intact, resulting from excessive axial length of the eyeball or excessive curvature of the cornea or lens, which causes light rays to focus in front of the retina rather than on it.[1][2][3] Affecting approximately 30-37% of the global population as of recent estimates, myopia prevalence varies significantly by region, with rates exceeding 60% in parts of East Asia among young adults compared to around 23-40% in Europe, and is projected to reach 50% worldwide by 2050 due to urbanization, increased near work, and reduced outdoor time.[4][5][6] Empirical evidence indicates that while genetic factors contribute to susceptibility, environmental influences—particularly prolonged near-focus activities such as reading, excessive smartphone use, video gaming, and other screen-based activities, and insufficient exposure to natural light—drive the axial elongation underlying myopia progression, as demonstrated in longitudinal studies and animal models of visual deprivation.[7][8][9][10] High myopia, defined as greater than -6 diopters, elevates risks for complications such as retinal detachment, myopic macular degeneration, and glaucoma, underscoring the public health implications of its epidemic rise. Although symptoms are effectively managed in most cases through correction via spectacles, contact lenses, or refractive surgery, there is no scientific evidence that myopia can be reversed or cured through eye exercises or practices such as viewing distant objects without glasses. Progression may be slowed in children by increased time outdoors and natural light exposure.[11][3][12][13]

Clinical Presentation

Signs and Symptoms

Myopia, or nearsightedness, is characterized by difficulty seeing distant objects clearly while near vision remains intact.[14][15] This refractive error results in images focusing in front of the retina, leading to blurred distance vision.[7] Common symptoms include eye strain, headaches, and squinting to sharpen focus on faraway targets.[16][15] Patients may report fatigue after tasks requiring prolonged distance viewing, such as driving or watching television.[7] In children, subtle behavioral indicators often precede formal diagnosis, such as holding books or screens excessively close to the face or complaints about not seeing classroom blackboards or sports details from afar.[17][18] These signs reflect compensatory habits to overcome visual deficits.[7] High myopia, defined as greater than -6 diopters, may present with additional risks like floaters from vitreous changes or early cataracts, though the primary symptom remains uncorrected distance blur.[7][19] Nocturnal myopia (also known as night myopia) refers to a temporary increase in nearsightedness observed in low-light conditions. It can cause exacerbated blur in low-light conditions primarily due to shifts in accommodation, where the eye tends to accommodate more in dim light. Additionally, pupil dilation in low light allows more light rays, including peripheral ones, to enter the eye, increasing spherical aberration and light scatter within the eye. This amplifies the effects of even mild existing refractive errors like myopia or astigmatism, making distance vision noticeably blurrier and lights appear with halos, streaks, or starbursts at night, even when daytime vision is clear. These effects are transient and reversible in brighter conditions or with appropriate correction.[20] Without correction, chronic symptoms can impair daily activities and quality of life.[15]

Classification by Type and Severity

Myopia is classified into several types based on anatomical, etiological, and clinical features. Anatomically, it is categorized by the primary optical mechanism causing the refractive error: axial myopia, resulting from excessive elongation of the eye's axial length (with each 1 mm increase typically producing a 3 diopter myopic shift); curvature myopia, due to excessive corneal or lenticular curvature; and index myopia, arising from alterations in the refractive index of the ocular media, such as in diabetes or nuclear cataracts (though rare).[7][21] Etiologically, myopia includes simple or physiologic forms, which are non-pathologic and often school-age onset without structural damage; pathologic or degenerative myopia, characterized by high refractive errors (typically > -6 diopters) accompanied by posterior staphyloma, lacquer cracks, or myopic maculopathy leading to potential vision loss; and secondary or induced types, such as those from drugs (e.g., sulfonamides), accommodative spasm, or postoperative changes.[20][21] Transient variants, including pseudomyopia from ciliary muscle spasm or nocturnal myopia in low light, are temporary and reversible upon addressing the trigger.[20] Severity is primarily graded by the spherical equivalent refractive error under cycloplegia to minimize accommodation effects. The International Myopia Institute proposes standardized thresholds: myopia as ≤ -0.50 diopters (D), low myopia as > -6.00 D to ≤ -0.50 D, and high myopia as ≤ -6.00 D, with pathologic myopia distinguished not solely by degree but by structural ocular changes conferring risks like retinal detachment.[21] Alternative clinical categorizations include mild (-0.50 D to -4.00 D), moderate (-4.00 D to -8.00 D), and severe (> -8.00 D), though thresholds vary across guidelines, with high myopia often starting at > -6.00 D and associated with elevated complication risks. Severe myopia (e.g., -13 to -14 diopters) is typically not classified as a disability if correctable to good visual acuity (≥ 0.8); disability recognition generally applies only if permanent complications, such as retinal degeneration, result in uncorrectable vision loss.[22][23][7][20]
Severity CategoryDiopter Range (Spherical Equivalent)Key Characteristics
Low/Mild≤ -0.50 D to > -6.00 DGenerally physiologic; low risk of pathology; correctable with standard optics.[21][20]
High/Severe≤ -6.00 DIncreased axial length; higher incidence of complications like choroidal neovascularization.[7][21]
PathologicOften > -8.00 D with structural changesDegenerative retinal/choroidal alterations; requires monitoring beyond refraction.[7]
In addition to the International Myopia Institute's thresholds and alternative categorizations listed, many eye care sources and organizations use the following approximate classifications for myopia severity:
  • Mild myopia: -0.25 to -3.00 diopters (some sources extend mild up to -1.50 or -2.00 D)
  • Moderate myopia: -3.00 to -6.00 diopters (or starting from -2.25 or -1.50 in some classifications)
  • High/severe myopia: greater than -6.00 diopters
These variations reflect differences in clinical guidelines, such as those from the American Academy of Ophthalmology and other optometric sources. Epidemiological data from large cohorts of myopic individuals often show mean or median spherical equivalent refractive errors in the range of -2.5 to -2.8 diopters (for example, means of -2.8 ± 2.3 D in large adult populations and medians around -2.50 D in other studies). This indicates that prescriptions around -2.75 diopters fall within the typical and most common range for nearsightedness, generally considered moderate or borderline mild/moderate depending on the classification system used. Approximate correspondences between the degree of myopia and uncorrected visual acuity are sometimes provided in popular health education materials and folk references. These are not strict medical standards and can vary considerably due to individual differences such as astigmatism, pupil size, lighting conditions, and other ocular factors. For example, in myopia of 500 degrees (-5.00 D), uncorrected visual acuity has no fixed value due to such individual variations (including pupil size, astigmatism, and axial length) and typically ranges from 0.05 to 0.2, with approximately 0.15 being a common value observed in clinical experience. These figures serve only as clinical references and are not absolute; professional verification through comprehensive eye examination is required for accurate assessment. Such approximations supplement the severity classification by illustrating the potential functional impact of uncorrected refractive error on distance vision. A commonly referenced approximate table includes:
Myopia Degree (diopters)Approximate Uncorrected Decimal Visual AcuityApproximate Log Visual Acuity (5-point scale)
1000.84.9
2000.54.7
3000.34.5
4000.254.4
4500.24.3
5000.154.2
5500.124.1
6000.14.0
6500.14.0
These values are approximate and drawn from popular sources; actual uncorrected visual acuity may differ significantly.

Pathologic Myopia (Degenerative Myopia or Myopic Macular Degeneration)

Pathologic myopia, also known as degenerative myopia or myopic macular degeneration, is a severe form of myopia characterized by excessive axial elongation of the eyeball (typically axial length >26-26.5 mm or refractive error ≥ -6.00 D) leading to structural degenerative changes in the posterior eye segment, particularly the retina, choroid, and sclera. Unlike simple myopia, pathologic myopia involves progressive biomechanical stretching and thinning, resulting in potentially irreversible vision loss.[24] It affects approximately 0.9-3.1% of the global population, with higher rates in East Asia where high myopia is more prevalent. Pathologic myopia is a leading cause of irreversible visual impairment in working-age adults in some regions.[25] Key complications include:
  • Myopic maculopathy (myopic macular degeneration): Progressive chorioretinal atrophy, lacquer cracks, and choroidal neovascularization (CNV), often causing central vision loss.
  • Retinal detachment: Due to stretched and thinned retina.
  • Earlier onset of cataracts and glaucoma.
  • Other: Macular holes, posterior staphyloma.
Meta-analyses show significantly elevated risks; for example, high myopia carries an odds ratio of 845 for myopic macular degeneration compared to emmetropia, with substantial risks even in low/moderate myopia.[26] Progression rates vary, but in eyes with existing pathologic changes, progression occurs in about 17% over 6 years, with new onset in approximately 1.2% of myopic eyes over similar periods. Over longer follow-up (10-12 years), 10% or more may experience onset or worsening of macular degeneration.[27] Vision outcomes include progressive decline in a significant proportion of cases (around 40% in some cohorts); in CNV subsets, even with treatment, vision may deteriorate, with cumulative risks of moderate to severe impairment or blindness (e.g., up to 25% blindness at 10 years in some studies). Atrophy and scarring are often irreversible. Management focuses on early detection through regular examinations (including OCT and fundus imaging), treatment of complications such as anti-VEGF injections for CNV to stabilize vision, surgical intervention for retinal detachment, and supportive low-vision aids. No cure exists for the degenerative changes themselves; emphasis is on preventing progression through myopia control strategies in early stages.

Pathogenesis

Ocular Mechanisms

Myopia arises primarily from axial elongation of the eyeball, which shifts the retinal plane posterior to the focal point of incoming light rays, resulting in blurred distance vision. This elongation disrupts emmetropization, the developmental process that normally calibrates ocular growth to achieve refractive neutrality. In emmetropic eyes, axial length approximates 23-24 mm in adults, but myopic eyes exceed this, with each millimeter increase corresponding to roughly 3 diopters of myopia.[28][29] The sclera plays a central role in accommodating this elongation through biomechanical remodeling, transitioning from a rigid structure to one capable of expansion. During myopia progression, scleral thickness decreases, particularly posteriorly, while extracellular matrix (ECM) components like collagen fibrils exhibit reduced diameter and packing density, diminishing tensile strength. This is accompanied by upregulated matrix metalloproteinases (MMP-2 and MMP-3) and decreased tissue inhibitors of metalloproteinases (TIMPs), yielding net ECM degradation and scleral thinning.[30][31] Proteoglycan alterations, including reduced lumican and biglycan, further weaken the scleral matrix, facilitating passive distension under intraocular pressure.[30] Retinal and choroidal tissues contribute via growth-regulating signals in response to optical defocus. Hyperopic defocus—where the image plane falls behind the retina—triggers local retinal pathways that promote elongation, potentially through dopamine and glucagon signaling deficits. The choroid thins rapidly in early myopia, reflecting vascular and stromal changes that may modulate scleral perfusion and metabolite delivery. Retinal pigment epithelium (RPE) ion transport and growth factor release, such as those involving vascular endothelial growth factor (VEGF), influence adjacent choroidal and scleral remodeling.[32][33] Corneal and lenticular changes are minor contributors, with corneal power typically flattening slightly (0.2-0.5 diopters) in myopes, insufficient to explain refractive shifts. In high myopia, the globe assumes a prolate ellipsoid shape, stretching photoreceptor arrays and thinning the retina, which elevates risks for complications like macular degeneration. Axial elongation persists into adulthood in myopic individuals, contributing to refractive progression that averages around 1 diopter between ages 20 and 30 in some cases, with higher baseline myopia increasing the risk of continued progression, while rates decelerate with age.[34][35][36][37]

Genetic Factors

Heritability estimates for myopia, derived from twin and family studies, indicate a substantial genetic component, with narrow-sense heritability ranging from 0.60 to 0.94 for refractive error and axial length in various populations.[38] Monozygotic twins exhibit concordance rates for myopia significantly higher than dizygotic twins, supporting additive genetic influences over shared environment alone.[39] These studies consistently demonstrate that genetic factors account for 70-90% of variance in myopia susceptibility, particularly in low to moderate cases, though estimates vary by age, ethnicity, and myopia severity.[40] Genome-wide association studies (GWAS) have identified over 500 common genetic variants associated with refractive error and myopia, primarily through large-scale meta-analyses involving hundreds of thousands of participants.[41] These loci, often near genes involved in eye development, scleral remodeling, and neuronal signaling (e.g., those regulating extracellular matrix or dopamine pathways), each confer small effect sizes but collectively explain up to 15-20% of phenotypic variance.[42] High myopia shows enrichment for rare variants, with exome sequencing revealing pathogenic mutations in genes like those implicated in syndromic forms (e.g., collagen-related genes), contributing to severe axial elongation.[43] Polygenic risk scores (PRS), aggregating effects from GWAS-derived variants, predict myopia onset and progression with moderate accuracy, achieving area under the receiver operating characteristic curve (AUROC) values of 0.65-0.70 in independent cohorts.[44] Recent PRS models, refined for specific ancestries such as East Asian populations, enhance detection of high myopia risk in children, though predictive power remains limited without integration of non-genetic factors.[45] Overall, myopia's genetic architecture reflects a polygenic threshold model, where cumulative liability from common and rare variants predisposes individuals, underscoring the absence of single-gene determinism except in rare familial cases.[46] Family and twin studies show that children with one myopic parent have an approximately 1.5 to 3 times higher risk of developing myopia compared to those with no myopic parents, with odds ratios around 1.4–2.0 in some cohorts. The risk increases further (often 2.5–6 times) if both parents are myopic. These elevated risks stem from polygenic inheritance involving multiple genetic variants that increase susceptibility, interacting with environmental factors like near work and limited outdoor time. Parental myopia serves as a proxy for genetic loading, and stronger familial patterns (e.g., multiple affected siblings) indicate higher transmission potential. However, these are probabilistic risks, not deterministic, and modifiable lifestyle factors can substantially mitigate outcomes even in high-genetic-risk families.

Environmental Factors

Increased time spent on near work activities, such as reading or using digital screens, is associated with higher odds of myopia development and progression, with meta-analyses reporting an odds ratio of 1.14 (95% CI: 1.08-1.20) for additional near work time.[47] This association holds across cohort and cross-sectional studies, though causation remains debated due to potential confounding by factors like education intensity.[48] Prolonged near work may induce accommodative stress or alter retinal signaling, contributing to axial elongation of the eye.[49] Greater time outdoors, particularly exposure to natural sunlight, consistently shows a protective effect against myopia onset, with multiple reviews finding reduced incidence and slower progression in children spending more than 2 hours daily (~14 hours per week) outside.[50] For instance, interventions increasing outdoor time by 1-2 hours per day lowered myopia risk by up to 50% in randomized trials, independent of ethnicity or baseline refractive error.[51] The mechanism likely involves higher-intensity light (typically >1,000–2,000 lux outdoors) stimulating retinal dopamine release, which inhibits scleral remodeling and axial growth.[52] Even short bursts of continuous sunlight exposure (≥15 minutes at ≥2,000 lux) correlate with less myopic shift and slower progression, as measured by wearable devices.[53] Higher educational attainment and intensive schooling environments correlate strongly with elevated myopia prevalence, with studies showing odds ratios up to 2-3 times higher in populations with prolonged indoor academic demands.[54] This link persists after adjusting for genetics, as evidenced by birth month analyses where later school entry reduces myopia risk due to more pre-school outdoor exposure.[55] Urbanization amplifies these effects through reduced green space access and increased near work, with rural-urban prevalence gaps exceeding 20% in multiple cohorts.[56] Digital screen time, a modern variant of near work, shows dose-dependent risks, with a systematic review and dose-response meta-analysis indicating that each additional hour of daily digital screen time is associated with 21% higher odds of myopia (OR 1.21; 95% CI 1.13-1.30). Prolonged use of smartphones, video games, and other digital devices is associated with reduced blink rates (often halved during focused screen viewing), leading to tear film instability, dry eyes, and symptoms of digital eye strain including eye fatigue, irritation, and transient blurred vision (pseudomyopia). While these acute effects are generally reversible, chronic exposure—particularly in children and adolescents—may contribute to sustained accommodative demand and axial elongation, potentially accelerating myopia progression. Such changes are typically gradual and multifactorial, influenced by overall near work duration, reduced outdoor time, and other environmental factors.[10][57][58]

Gene-Environment Interactions and Debates

Twin and family studies consistently demonstrate high heritability for myopia, with estimates ranging from 0.60 to 0.90, indicating that genetic factors account for a substantial portion of refractive error variation within populations.[59] However, the explosive rise in myopia prevalence—such as from approximately 10-20% in European cohorts born in the 1950s to over 50% in those born after 1990—occurs too rapidly to be attributable to shifts in gene frequencies, underscoring the necessity of environmental modifiers acting on genetic predispositions.[56] Polygenic risk scores derived from genome-wide association studies (GWAS), encompassing over 450 loci associated with myopia, interact with environmental exposures; for instance, individuals with elevated genetic risk show amplified refractive progression when exposed to high levels of near work or education, as evidenced by longitudinal cohort data.[60][61] These interactions likely operate through pathways where genetic variants influence scleral remodeling or retinal signaling, modulated by environmental cues like reduced natural light exposure, which may suppress dopamine release and alter emmetropization. Mendelian randomization analyses, leveraging genetic variants as instrumental variables, provide causal evidence that prolonged education—a proxy for intensive near work—elevates myopia risk independently of confounding socioeconomic factors.[46] Conversely, outdoor time exerts a protective effect, with randomized trials showing 2-3 hours daily reducing incidence by up to 50% in high-risk groups, suggesting gene-dependent responsiveness to light-mediated mechanisms.[46] Longitudinal studies have identified a positive association between the pubertal growth spurt, measured by peak height velocity, and myopia progression in teenagers. Earlier or more pronounced peak height velocity is linked to earlier myopia onset, earlier peak axial length elongation, and faster myopia progression. In the Singapore Cohort Study of the Risk Factors for Myopia (SCORM), children with earlier peak height velocity experienced earlier myopia onset and peak axial length velocity, with similar patterns in both genders but occurring earlier in girls.[62] Recent research further shows that myopia control treatments blunt axial elongation during these growth periods but do not fully decouple it from systemic growth, with the association persisting and appearing particularly strong in girls aged 10-12 years.[63] Debates center on the relative primacy of genetic versus environmental drivers: proponents of a predominantly genetic etiology argue that heritability metrics and stable familial patterns indicate environment primarily accelerates progression in genetically susceptible individuals, rather than initiating de novo cases.[64] Critics counter that population-level epidemics, particularly in urbanizing East Asia where prevalence exceeds 80% among young adults, reflect causal environmental dominance, as genetic evolution cannot account for decadal surges; this view is bolstered by animal models demonstrating environmentally induced axial elongation absent in controls.[65][66] Resolution remains elusive, with calls for larger-scale interaction studies using polygenic scores and environmental tracking to disentangle effects, though methodological challenges like unmeasured confounders persist.[46] Emerging evidence from multi-ancestry GWAS hints at ancestry-specific interactions, where East Asian genomes may confer heightened vulnerability to modern visual demands.[61]

Epidemiology

Global Prevalence and Projections

The global prevalence of myopia across all age groups was estimated at 22.9% (1.4 billion people) in 2000, rising to approximately 30% (around 2.6 billion people) by the early 2020s, reflecting a sustained upward trend driven primarily by increases among younger populations.[67][6] Among children and adolescents specifically, meta-analyses of studies spanning 1990 to 2023 report a pooled prevalence escalating from 24.3% to 35.8%, with current estimates around 30.5% globally.[4][68] These figures derive from systematic reviews aggregating cycloplegic refraction data across diverse populations, though variations exist due to differences in diagnostic criteria and underreporting in low-resource regions.[4] Projections to 2050, modeled on age-, gender-, and ethnicity-stratified trends from 1990 onward, forecast that myopia will affect nearly 50% of the world's population (approximately 4.8 to 5 billion individuals), representing a roughly twofold increase from early 21st-century levels.[67][69] High myopia (typically defined as ≤ -6 diopters) is anticipated to reach 10% prevalence globally, heightening risks of associated complications like retinal detachment.[67] For children and adolescents, prevalence could exceed 39-40% by mid-century, potentially impacting over 740 million individuals in that demographic alone, assuming continuation of current urbanization and lifestyle patterns without widespread interventions.[70][71] These estimates, from meta-regression analyses, carry uncertainties related to demographic shifts and potential mitigation efforts, such as increased outdoor activity, but underscore the trajectory toward a public health challenge of unprecedented scale.[67][4] In addition to prevalence rates, studies of myopic populations indicate that the condition is most commonly mild to moderate. Large-scale data show average spherical equivalent refractive errors around -2.5 to -2.8 diopters among myopes, with many individuals having prescriptions in the -1.00 to -4.00 D range, making values such as -2.75 D typical for nearsighted individuals.

Regional and Demographic Variations

Myopia prevalence varies markedly by region, with East and Southeast Asia exhibiting the highest rates globally. In urban East Asian populations, myopia affects over 80% of young adults, driven by high incidence in school-aged children. For example, Hong Kong has a high prevalence of myopia among schoolchildren, with overall rates of 37.7% in primary students (increasing with age from 13.3% in grade 1 to 54.7% in grade 6) and 61.5% in 12-year-olds. High myopia (≤ -6.0 D or axial length ≥26.5 mm), a major risk factor for pathologic myopia (characterized by degenerative changes like myopic maculopathy), has a prevalence of about 1-4% in schoolchildren, increasing with age; these high rates of high myopia elevate the risk of associated complications such as visual impairment.[72][73] In contrast, rates in Europe are substantially lower, with a meta-analysis reporting childhood and adolescent prevalence ranging from 11.9% in Finland to 49.7% in Sweden, influenced by age and national differences.[74] In the United States and Europe, adult myopia prevalence hovers around 30-33%, far below East Asian figures.[75] Regions like sub-Saharan Africa and the Eastern Mediterranean show even lower childhood rates, with pooled prevalence of 5.23% in the latter from 2000-2022 studies.[76] Demographic factors further delineate variations. Ethnically, East Asians consistently demonstrate the highest myopia rates, exceeding those of white Europeans by more than twofold in comparable age groups; South Asian children face a ninefold risk relative to white Europeans, while black African Caribbeans experience a threefold increase.[77][78] Gender disparities appear in several contexts, with females showing higher prevalence than males, such as 4.90% versus 3.94% in Eastern Mediterranean schoolchildren.[76] Age-related patterns reveal escalating prevalence through childhood and adolescence. Myopia in preschool children (typically ages 3-6 years) has a prevalence of about 5% and is less common than in school-aged children but shares similar multifactorial causes. It results primarily from axial elongation of the eyeball (axial myopia) or, less commonly, a steeply curved cornea, focusing light in front of the retina instead of on it. Key risk factors include genetic predisposition (especially parental myopia), limited time outdoors, and excessive near work such as reading or screen time. Prevalence rises from under 3% in ages 0-4 to over 67% in late teens in aggregated global data, stabilizing in adulthood.[79][80]
Ethnicity (Children)Myopia Risk Relative to White EuropeansSource
East Asian>2-fold[78]
South Asian9-fold[77]
Black African Caribbean3-fold[77]

Correlations with Socioeconomic and Behavioral Factors

Higher educational attainment is consistently associated with increased myopia prevalence. A 2022 analysis of over 1 million Chinese students aged 6-18 years found that each additional year of schooling correlated with a 0.28 diopter increase in myopia progression, independent of age, suggesting education itself as a causal risk factor through intensified near work demands.[81] Cross-national studies further confirm this, with higher Programme for International Student Assessment (PISA) scores—indicative of educational intensity—linked to elevated myopia rates among adolescents, as seen in a 2023 review spanning multiple countries.[82] A 2025 preprint examining U.S. data reported that educational level mediates 20-24% of the association between income-to-poverty ratio and myopia, underscoring education's role in overriding direct socioeconomic effects.[83] In Hong Kong, a region with notably high myopia prevalence linked to intense educational environments, overall myopia prevalence among primary schoolchildren was 37.7%, increasing with age from 13.3% in grade 1 to 54.7% in grade 6. High myopia (≤ -6.0 D or axial length ≥26.5 mm) affected approximately 0.94% to 1.85% across grades, with some studies reporting rates up to 61.5% among 12-year-olds. Identified risk factors for myopia development included older age, better academic performance (as reflected in class ranking), and lack of routine eye checks. High myopia elevates the risk of pathologic myopia, characterized by degenerative changes such as myopic maculopathy, which can lead to visual impairment.[72][73] Socioeconomic status (SES) exhibits context-dependent correlations with myopia, often confounded by urbanization and access to resources. In urban Chinese schoolchildren, higher urbanization levels independently raised myopia incidence by up to 1.5-fold, aligning with denser populations and reduced green space exposure typical of higher-SES urban settings.[84] Conversely, some studies in lower-income areas report elevated prevalence, such as 60.7% myopia rates among low-SES students in 2022 screenings, potentially due to limited preventive interventions or nutritional deficits rather than behavioral patterns alone.[85] In European cohorts, low maternal education and non-European ethnicity independently predict higher odds of myopia in 6-year-olds, with environmental adjustments explaining much of the SES gradient. Behavioral factors, particularly near work and outdoor time, drive much of the observed correlations. Prolonged near work—defined as activities like reading or screen use at distances under 30 cm—shows dose-dependent risk, with a 2022 study of Australian children linking over 2 hours daily to 1.5-2 times higher myopia odds, mediated by accommodative lag and peripheral defocus.[86] Increased outdoor time exerts a protective effect, with meta-analyses indicating that 1-2 additional hours daily in childhood reduces myopia onset risk by 13-50%, attributable to higher light intensities (over 10,000 lux) promoting dopamine release and emmetropization.[87][51] These behaviors intersect with SES, as higher-education families report greater near work but potentially modifiable through policy interventions like recess extensions.[88]

Diagnosis

Examination Methods

The diagnosis of myopia requires a comprehensive ocular examination to determine refractive error, typically defined as a spherical equivalent of -0.50 diopters or more in either eye under cycloplegic conditions. Initial screening involves assessing uncorrected distance visual acuity using standardized charts such as the Snellen chart (measuring ability to resolve letters at 20 feet) or the more precise ETDRS logMAR chart, which quantifies vision loss correlating with myopic blur for distant objects.[89] Best-corrected visual acuity is then evaluated after refraction to confirm the refractive nature of the impairment and rule out other causes like media opacities.[89] Objective refraction precedes subjective refinement, employing autorefractors that use infrared light to analyze the eye's focusing power via Scheiner's principle, providing rapid estimates of sphere, cylinder, and axis.[20] Streak retinoscopy offers an alternative objective method, where the examiner observes the reflex from a retinoscope beam on the patient's retina to neutralize refractive error with trial lenses, particularly useful in non-cooperative patients or to validate autorefraction results.[90] Cycloplegic refraction, achieved with agents such as 1% cyclopentolate or 1% tropicamide instilled 20-30 minutes prior, is essential in children under 18 and young adults to paralyze accommodation, preventing pseudomyopia from latent hyperopia or over-minusing; studies show non-cycloplegic methods can underestimate myopia by up to 0.75 diopters in pediatric populations.[90] [89] Biometric measurements complement refraction, with axial length assessed via optical biometry devices like partial coherence interferometry (e.g., IOLMaster 700, measuring from cornea to retinal pigment epithelium with sub-10-micrometer precision), as elongated axial length exceeding 25 mm strongly correlates with myopic refraction (r ≈ -0.8).[91] Corneal curvature is evaluated using keratometry or Placido-disc topography to calculate keratometry readings (typically 42-44 diopters in emmetropia) and exclude irregular astigmatism or ectatic disorders.[20] Slit-lamp biomicroscopy inspects anterior segment structures for anomalies, while dilated funduscopy or optical coherence tomography surveys the posterior segment for staphylomata, lacquer cracks, or choroidal thinning indicative of pathologic myopia.[89] Intraocular pressure measurement via tonometry is included to screen for coincidental glaucoma risk heightened in high myopia.[89]

Progression Assessment

To prevent progression to high myopia, guidelines recommend initiating vision screening from age 3, with eye health checks every 6-12 months including axial length measurement and cycloplegic refraction to enable early detection and intervention.[92][93] Progression of myopia, particularly in children and adolescents, is assessed through serial measurements of refractive error and ocular biometry to detect changes indicative of worsening axial elongation or hyperopic defocus.[93] Myopia typically progresses most rapidly between ages 6 and 12, with annual refractive shifts often exceeding -0.50 diopters (D) in untreated cases, though progression can continue or accelerate during adolescence in association with the pubertal growth spurt. Earlier or more pronounced peak height velocity during puberty is linked to earlier myopia onset, earlier peak axial length elongation, and faster myopia progression, with stronger associations observed in girls during ages 10-12; this relationship persists even with myopia treatments, though treatments may blunt the effect.[62][63] necessitating regular monitoring to evaluate stabilization or response to interventions.[94] Although myopia progression is most rapid during childhood and adolescence, it can continue into young adulthood, albeit at slower rates. According to the International Myopia Institute (IMI) report on onset and progression in young adults, clinically meaningful progression persists into early adulthood, averaging approximately -1.00 D between ages 20 and 30 years, with annual rates typically -0.10 to -0.25 D/year in 18-25 year olds, decreasing to less than -0.1 D/year after age 25. Higher baseline myopia is associated with greater absolute progression.[95] Studies show variable proportions: in one cohort from age 20 to 28, 37.8% experienced a myopic shift of ≥0.50 D, with myopia incidence of 14% in non-myopes. Other data indicate 10-20% of young adults show significant progression (e.g., ≥0.50 D/year or ≥1.00 D over 5 years), with higher rates in early 20s declining thereafter. For mild myopia (e.g., -0.50 to -1.50 D) noticed in the mid-20s, the risk of substantial worsening is generally lower than in higher degrees.[96] Factors influencing adult progression include younger age (strongest predictor), parental myopia, female sex, East Asian ethnicity, prolonged near work, limited outdoor time, and high visual demand (e.g., academic environments). Progression is due to continued axial elongation, though less pronounced than in childhood. Most individuals with mild adult-onset or late-noticed myopia stabilize with minimal further change, but regular monitoring is recommended. Axial length elongation serves as the gold standard metric, as it correlates more directly with true myopic progression than refraction alone, with increases of 0.3 mm or more per year signaling active advancement.[97][98] Cycloplegic refraction remains essential for accurate assessment, as non-cycloplegic methods can underestimate myopia due to accommodative effort, especially in younger patients.[99] This involves instilling agents like 1% tropicamide (two drops) to paralyze accommodation, followed by autorefraction or retinoscopy 30-45 minutes later to determine the spherical equivalent refractive error.[93] Progression is quantified as a myopic shift of ≥0.50 D over 6-12 months, though smaller changes may warrant attention in high-risk groups.[100] Guidelines emphasize cycloplegic autorefraction at baseline and follow-ups to ensure comparability, avoiding overestimation of stability from pseudomyopia.[101] Ocular biometry, using devices such as partial coherence interferometry (e.g., IOLMaster), measures axial length from the corneal apex to the retinal pigment epithelium with precision to 0.01 mm.[102] This non-invasive technique outperforms refraction for tracking subtle progression, as refractive changes can be influenced by corneal or lenticular variations, whereas axial elongation directly reflects scleral remodeling.[103] Annual biometry is recommended alongside refraction to monitor treatment efficacy, with tools like optical coherence tomography enabling even finer resolution in advanced settings.[104] Clinical protocols from bodies like the International Myopia Institute advocate biannual cycloplegic refractions and annual axial length assessments for progressing myopia, adjusting frequency based on baseline severity and age.[105] In practice, progression thresholds trigger interventions, such as low-dose atropine or specialized lenses, while stable cases (e.g., <0.25 D or <0.2 mm change yearly) may extend intervals to yearly exams.[93] Corneal topography or fundus evaluation supplements these core metrics if keratoconus or other comorbidities are suspected, ensuring comprehensive risk stratification.[94]

Prevention

Outdoor Time and Natural Light Exposure

Epidemiological studies have consistently demonstrated that greater time spent outdoors during childhood is associated with a reduced risk of myopia onset. A longitudinal analysis of over 2,000 children found that increasing daily outdoor time from 1 to 3 hours could lower myopia risk by approximately 50%.[87] Meta-analyses of clinical trials confirm a dose-response relationship, with each additional hour of outdoor activity correlating to a slightly lower incidence of myopia and smaller myopic shifts in refractive error, particularly among non-myopic children.[106][51] School-based cluster randomized trials provide causal evidence for this protective effect. In one intervention involving primary school students, adding 40 minutes of daily outdoor class time reduced the two-year cumulative incidence of myopia from 31.9% in controls to 21.2% in the intervention group.[107] Another trial reported that an extra 80 minutes outdoors per day decreased myopia incidence by 9.3% over a shorter follow-up period compared to standard schedules.[53] These findings hold across diverse populations, including in high-prevalence regions like East Asia, where policy changes mandating additional outdoor breaks have yielded similar reductions in myopia progression rates.[50] Objective measurements from a 2024 cohort study using smartwatch data in children demonstrated that continuous outdoor exposure patterns of ≥15 minutes at light intensities of ≥2,000 lux were associated with slower myopia progression, as indicated by reduced myopic shift in refraction.[53] The underlying mechanism appears tied to the high-intensity natural light encountered outdoors, which stimulates retinal dopamine release and signaling pathways that inhibit axial elongation of the eye. Outdoor illuminance levels, often exceeding 10,000 lux, far surpass typical indoor lighting (under 500 lux), triggering dose-dependent dopamine D1 receptor activation in retinal bipolar cells of the ON pathway, which suppresses form-deprivation and lens-induced myopia in animal models.[108][109] No specific universal lux level is recommended for indoor lighting to prevent myopia progression, but evidence suggests higher levels are beneficial. One study showed increasing classroom lighting from ~100 lux to 500 lux reduced myopia incidence. Levels above 1,000 lux are considered protective against myopia onset in multiple studies. Supplemental bright light therapy at 10,000 lux has been tested in trials to slow progression. Primary prevention focuses on outdoor time with natural light exceeding 1,000–10,000 lux. In humans, this light-induced dopamine surge aligns with circadian regulation of ocular growth, counteracting emmetropization signals disrupted by near work; however, these mechanisms primarily influence developing eyes in children and do not reverse existing myopia in adults, where the eye is fully developed and axial length is stable.[110] While effective for prevention, outdoor exposure shows modest effects on slowing progression in established myopia cases, with evidence stronger for preventing onset than slowing progression in those already myopic.[111] Public health guidelines increasingly recommend at least 2 hours of daily outdoor time (approximately 14 hours per week) with bright light exposure (>1,000–10,000 lux) for children and adolescents to help slow myopia progression and mitigate myopia risk, supported by evidence from cohort studies linking sustained exposure to long-term refractive stability.[112] However, benefits may vary by age, with stronger effects in younger children before puberty, although myopia progression can accelerate during the pubertal growth spurt in teenagers due to associations with earlier or more pronounced peak height velocity, which is linked to faster axial length elongation and myopia progression. Continued outdoor exposure remains important through adolescence to help mitigate these effects.[62][63][113] It is important to distinguish the evidence-based protective effects of time spent outdoors in natural light from unsubstantiated practices such as eye exercises or focusing on distant objects without corrective lenses. There is no scientific evidence that such methods can reduce refractive errors, reverse myopia, slow its progression, or eliminate the need for glasses. The American Academy of Ophthalmology has stated that eye exercises and vision training do not improve vision sharpness or correct refractive errors such as myopia, with no reliable evidence supporting their use for these purposes.[12][114]

Near Work and Screen Time Reduction

Near work activities, such as prolonged reading or close-focus tasks, have been associated with increased odds of myopia development in children and adolescents, with a meta-analysis of 27 studies reporting an odds ratio (OR) of 1.14 (95% CI: 1.08-1.20) for higher near work exposure.[115] [116] This association, while generally weak and subject to inconsistencies across studies due to confounding factors like outdoor time, is supported by dose-response patterns where each additional diopter-hour of near work per week correlates with a 2% increased myopia risk.[117] Reducing near work is thus proposed as a preventive measure, though direct causal evidence from isolated interventions remains limited, as most benefits are observed in combination with increased outdoor exposure.[118] Digital screen time exhibits a stronger dose-response relationship with myopia, where each additional hour per day is linked to a 21% higher odds of myopia in systematic reviews of children, with risk escalating nonlinearly beyond 1-4 hours daily.[10] [119] Children exceeding 3 hours of daily screen use show nearly fourfold higher myopia prevalence compared to those with minimal exposure, potentially exacerbated by reduced blinking, sustained accommodation, and associated indoor confinement. Excessive use of smartphones, video games (including interactive ones such as Mario Kart), and similar prolonged screen-based activities can intensify these effects, contributing to digital eye strain, temporary pseudomyopia (blurred distance vision due to accommodation spasm), dry eyes from reduced blinking, less outdoor time, and potential progression to permanent myopia through axial elongation. Such vision declines are typically gradual and multifactorial; sudden or rapid permanent changes in visual acuity (e.g., sharp drops from 1.5 to 0.5) require prompt medical evaluation, as excessive screen time alone rarely causes abrupt permanent loss.[120] Interventions targeting screen reduction, such as parental limits and school policies enforcing breaks, demonstrate feasibility in preschoolers, with short-term programs (under 6 months) effectively curbing usage by promoting alternative activities.[121] [122] Preschool children share similar risk factors for myopia development as older children, including excessive near work and screen time,[123] although the prevalence is lower, affecting about 5% of preschoolers.[124] Guidelines recommend capping recreational screen time at 1-2 hours daily for school-aged children while integrating breaks from near work, such as resting for 10 minutes every 30-40 minutes by gazing into the distance or closing eyes, which studies indicate may help mitigate myopia risk more effectively than shorter intervals.[125] The 20-20-20 rule—20-second breaks every 20 minutes—provides insufficient relief for axial elongation compared to longer defocus periods.[126] [127] Behavioral strategies, including homework limits, device-free zones, avoiding eye rubbing to prevent corneal distortion, and steering clear of ocular trauma, align with public health efforts to mitigate progression, particularly in high-prevalence regions like East Asia, where near work demands exceed 10 hours daily for students; annual eye examinations at specialized facilities are advised for monitoring.[128] [129] However, isolated screen or near work reductions yield modest effects (e.g., 10-20% slowdown in progression rates in cohort studies), underscoring the need for multifaceted approaches rather than reliance on time limits alone.[130][131]

Pharmacologic and Optical Prophylaxis

Low-dose atropine eye drops represent the primary pharmacologic intervention for slowing myopia progression in children, with concentrations of 0.01% to 0.05% administered nightly demonstrating efficacy in randomized controlled trials and meta-analyses. A 2024 meta-analysis of studies involving children with premyopia or early myopia found that atropine delayed myopia onset and reduced axial elongation by 0.09-0.23 mm over 1-2 years compared to placebo, with low adverse event rates such as mild photophobia in under 10% of cases.[132][133] Another meta-analysis confirmed progression slowing of 0.5-1.0 diopters over 6-36 months across doses, attributing benefits to muscarinic receptor inhibition that modulates scleral remodeling without significant systemic effects at low concentrations.[134] Concentrations around 0.05% offer an optimal efficacy-safety profile, outperforming 0.01% in some trials while avoiding the blurred vision and near accommodation loss seen with 1% atropine.[135] Evidence from 2025 supports prophylactic use in at-risk premyopic children aged 6-10 years, reducing incidence by up to 50% over 2 years, though rebound progression may occur upon discontinuation, necessitating long-term adherence.[136] Side effects remain minimal at these doses, with meta-analyses reporting adverse events in 5-15% of users, primarily transient pupil dilation.[137] Optical prophylaxis employs specialized lenses to create peripheral myopic defocus, aiming to counteract the hyperopic defocus believed to drive axial elongation in emmetropizing eyes. Multifocal soft contact lenses with high add powers (+2.50 diopters) reduced myopia progression by 45-72% and axial elongation by 0.1-0.2 mm annually in randomized trials involving children aged 8-15 years, outperforming single-vision lenses and low-add multifocals.[138][139] The BLINK study, a National Eye Institute-sponsored trial, specifically showed +2.50 D add lenses slowed refraction change by 0.41 diopters over 3 years versus 0.24 diopters for single-vision controls.[140] Dual-focus contact lenses similarly demonstrated cumulative slowing over 6 years, with 36% less progression than controls.[141] Defocus-incorporated spectacle lenses, such as those with multiple segments (DIMS) or peripheral defocus designs, have achieved 50-60% reduction in progression in Asian cohorts, with 2-year trials reporting 0.13 mm less axial growth than progressive addition lenses.[142] Orthokeratology—rigid gas-permeable lenses worn overnight to flatten the central cornea—slows progression by 40-50% over 1-2 years by inducing peripheral defocus during the day, though efficacy varies with initial myopia severity and requires careful hygiene to mitigate infection risks.[143] These interventions maintain visual acuity comparable to standard correction, but long-term data beyond 3 years remain limited, and effects may wane in high myopes. A 2025 review of over 70 clinical trials emphasized that optical methods provide 30-60% average slowing, with contact lens options slightly superior to spectacles due to consistent peripheral blur delivery.[144] Combination therapies, such as atropine with multifocals, show additive benefits in preliminary studies but require further validation.[145] Essilor Stellest eyeglass lenses, which utilize Highly Aspherical Lenslet Target (H.A.L.T.) technology to generate a volume of myopic defocus, represent an additional defocus-incorporated spectacle lens design for myopia control. Clinical evaluations have demonstrated that Stellest lenses slow myopia progression by approximately 67% on average over two years in children compared to standard single-vision lenses. These lenses have recently been authorized for myopia control in children.Myopia Control in Children: Essilor Stellest Eyeglass Lenses Authorised | Scientific European Blue-cut (blue light blocking) spectacles do not effectively slow myopia progression in children. A randomized controlled trial in myopic schoolchildren aged 8–13 found no significant difference in refractive progression or axial length growth between those wearing blue-filtering lenses and standard single-vision lenses over 12 months.[146] The International Myopia Institute 2025 report on interventions for controlling myopia does not recommend blue light filtering lenses, focusing instead on proven spectacle designs such as defocus-incorporated multiple segments or aspherical lenslets that reduce progression by 20–60%, along with therapies like atropine and orthokeratology. Myopia progression is driven primarily by factors such as genetics, excessive near work, and limited outdoor time, not blue light from screens.[144]

Public Health Interventions

In regions with high myopia prevalence, governments have launched large-scale prevention programs emphasizing increased outdoor time. Taiwan's 'Daily 120' initiative (launched 2010) promotes at least 2 hours of daily outdoor activity in schools, yielding data showing reduced myopia incidence. Singapore's National Myopia Prevention Programme (2001 onward) includes early screenings and guidelines for outdoor activities to delay onset. China's 2018 national myopia program, involving multiple agencies, sets targets for reduced near-work (e.g., less homework for young children) and increased outdoor time, aiming to lower prevalence through systemic changes. These initiatives demonstrate how evidence of outdoor light's protective effects (e.g., 50% risk reduction with 2-3 hours daily) can inform policy when aligned with long-term societal benefits like workforce eye health.

Treatment

Corrective Lenses

Corrective lenses for myopia employ concave (minus) lenses to diverge parallel light rays entering the eye, shifting the focal point from in front of the retina to directly on it, thereby restoring emmetropic focus for distance vision.[147] This optical principle, known since the 13th century but refined in modern optometry, allows individuals with myopia to achieve clear vision without altering the eye's axial length.[127] Spectacles, the most common form, consist of ground glass or plastic lenses fitted into frames, prescribed in diopters negative to the degree of refractive error, typically ranging from -0.25 to -30.00 diopters in severe cases.[3] Spectacles provide safe, non-invasive correction with minimal risk of ocular complications, though they may introduce peripheral distortions or prismatic effects in high prescriptions exceeding -6.00 diopters.[148] Materials such as polycarbonate or high-index plastics reduce lens thickness and weight for stronger corrections, improving comfort and aesthetics.[149] Anti-reflective coatings minimize glare, while aspheric designs mitigate edge distortions, enhancing visual quality across the field.[149] Contact lenses offer an alternative by resting directly on the cornea, eliminating frame-related obstructions and providing a wider, undistorted field of view compared to spectacles.[150] Soft spherical hydrogel or silicone hydrogel lenses correct simple myopic refractive errors by incorporating the appropriate minus power, with replacement schedules varying from daily disposables to extended-wear monthly types.[151] Rigid gas-permeable (RGP) lenses, though less common for routine myopia, maintain sharper optics due to tear lens stabilization and are preferred for higher corrections or irregular corneas.[151] Toric contacts address concomitant astigmatism by stabilizing orientation with prism ballast or dynamic designs.[151] While contact lenses enhance peripheral vision and cosmetic appeal, they carry risks including microbial keratitis from poor hygiene, with incidence rates of 1-2 per 10,000 daily wearers annually, necessitating strict compliance with cleaning protocols.[148] Spectacles avoid such infections but can slip or fog in humid conditions, potentially reducing efficacy during activity.[148] Both modalities require annual refractions to adjust for progression, as correction addresses symptoms but not underlying elongation in progressing myopia.[127] In high myopia, lenses may induce chromatic aberration, visible as color fringing in peripheral views, more pronounced with spectacles.[3] Corrective lenses, including spectacles and contact lenses, are the primary non-invasive method to manage myopia symptoms by providing clear distance vision. However, they do not reverse the underlying axial elongation or cure myopia. There is no scientific evidence that eye exercises, focusing on distant objects without corrective lenses, or other non-prescribed visual practices can reduce refractive errors, improve myopia, or eliminate the need for corrective lenses. The American Academy of Ophthalmology states that there is no scientific evidence to suggest that eye exercises can prevent or cure myopia.[152] While traditional corrective lenses, such as standard spectacles and contact lenses, focus light centrally on the retina to provide clear distance vision, they often result in hyperopic defocus in the peripheral retina, which may contribute to axial elongation and myopia progression in susceptible individuals.[153] Specialized spectacle lenses designed for myopia control, such as those incorporating aspheric lenslets (e.g., Stellest lenses), aim to induce peripheral myopic defocus by shifting peripheral light rays to focus in front of the retina. This mechanism is thought to reduce emmetropization signals that promote eye growth, thereby slowing myopia progression. Clinical studies have demonstrated efficacy in reducing axial length elongation by 0.5 to 1.0 diopters over 1-2 years compared to single-vision lenses.[154][155]

Pharmacological Management

Low-dose atropine eye drops represent the primary pharmacological intervention for slowing myopia progression in children, typically administered nightly without cycloplegia at concentrations of 0.01% to 0.05%.[156] These agents, muscarinic receptor antagonists, inhibit axial elongation and refractive error worsening by mechanisms including reduced scleral hypoxia and choroidal blood flow modulation, though the exact pathways remain under investigation.[157] Randomized controlled trials, such as the Low-Concentration Atropine for Myopia Progression (LAMP) study, demonstrate that 0.05% atropine reduces progression by approximately 50-60% over two years compared to placebo, with dose-dependent effects where lower concentrations like 0.01% yield 30-50% reduction in axial length elongation.[158] Meta-analyses confirm these findings across diverse pediatric populations, with 0.01% atropine slowing mean spherical equivalent progression by 0.22-0.30 diopters annually versus 0.50-0.60 diopters in controls.[159] Higher concentrations (0.5-1%) achieve greater inhibition—up to 88% reduction—but are limited by side effects including photophobia, near vision blur, and accommodation loss, prompting a shift to low-dose regimens since the ATOM2 trial in 2012.[160] At 0.01%, adverse events are minimal, with photophobia reported in under 5% of cases and no significant rebound progression upon discontinuation after 2-3 years, unlike higher doses.[159] Guidelines from bodies like the American Academy of Ophthalmology endorse low-dose atropine for children aged 5-12 with progressive myopia exceeding -0.50 diopters annually, particularly in high-risk groups such as those of East Asian descent where baseline progression rates are elevated.[145] Efficacy varies by age, baseline refraction, and ethnicity, with stronger effects in younger children (under 9 years) and faster progressors; some studies report non-significance in slower-progressing cohorts.[161] Other agents like pirenzepine have shown limited promise in early trials but lack widespread adoption due to inferior efficacy and availability issues compared to atropine.[162] Pharmacological approaches do not reverse existing myopia or serve as vision correction substitutes, and long-term data beyond 3-5 years remain sparse, necessitating monitoring for sustained benefits.[163] As of 2025, no U.S. FDA-approved myopia-slowing drops exist, with atropine often compounded off-label, though investigational therapies like SYD-101 await resubmission following a complete response letter.[164]

Surgical Interventions

Surgical interventions for myopia primarily consist of corneal refractive surgeries, which aim to reshape the anterior corneal surface to reduce or eliminate the eye's refractive power and improve uncorrected visual acuity. These procedures are indicated for adults with stable myopia (typically -1.00 to -12.00 diopters, depending on the method and corneal parameters) who have adequate corneal thickness and no contraindications such as progressive disease, thin corneas, or ectasia risk factors.[165] The American Academy of Ophthalmology (AAO) guidelines emphasize patient selection based on preoperative topography, pachymetry, and refraction stability for at least one year to minimize complications like regression or haze.[166] LASIK involves creating a partial-thickness corneal flap with a femtosecond laser or microkeratome, followed by excimer laser ablation of the underlying stroma to flatten the central cornea. Efficacy indices show over 95% of myopic patients achieving uncorrected visual acuity of 20/40 or better at one year postoperatively, with predictability within 0.50 diopters of target refraction in 90-95% of cases.[167] Long-term studies indicate stability in low-to-moderate myopia (-6.00 diopters or less), but higher myopia cases exhibit greater regression, with 10-20% requiring enhancement by five years due to biomechanical changes and stromal remodeling.[168] Risks include flap dislocation (0.1-1%), dry eye syndrome (up to 30% transiently), and corneal ectasia (0.04-0.6%), particularly in undetected forme fruste keratoconus.[169] Photorefractive keratectomy (PRK) ablates the corneal epithelium and superficial stroma directly without a flap, allowing regeneration of the surface. It yields comparable efficacy to LASIK for myopia up to -6.00 diopters, with 92-96% achieving within 0.50 diopters of intended correction at 12 months, though slower visual recovery (1-2 weeks of discomfort) and higher initial haze risk (mitigated by mitomycin-C) are noted.[170] Long-term outcomes demonstrate sustained refractive stability, with lower ectasia rates than LASIK (approximately 20 per 100,000 eyes), making it preferable for thinner corneas or high-risk professions.[169] Small incision lenticule extraction (SMILE) uses a femtosecond laser to create and extract a stromal lenticule through a small 2-4 mm incision, preserving more anterior corneal nerves and biomechanics. For moderate-to-high myopia (-3.00 to -10.00 diopters), it achieves similar efficacy and safety to femtosecond LASIK, with 88-95% predictability and reduced dry eye incidence (10-20% lower than LASIK).[171] Five-year data confirm stability, though high myopia corrections (> -7.00 diopters) show increased higher-order aberrations and potential regression in 5-15% of cases.[172] For severe myopia exceeding laser ablation limits (typically > -12.00 diopters) or thin corneas, phakic intraocular lenses (pIOLs), such as iris-fixated or posterior chamber models, are implanted to add negative power without removing natural lens tissue. Long-term efficacy indices exceed 1.0 (postoperative uncorrected vision better than preoperative corrected), with 90% predictability and endothelial cell loss stabilizing below 1% annually after year one; however, risks include cataract formation (1-2% at 10 years) and elevated intraocular pressure.[173] These procedures do not halt axial elongation in progressing myopia and are contraindicated in children under 18 per FDA guidelines due to instability.[174] Overall complication rates across methods remain low (under 5% vision-threatening), but lifelong monitoring for ectasia or endothelial changes is required.[175]

Orthokeratology and Emerging Methods

Orthokeratology involves the overnight wear of specially designed rigid gas-permeable contact lenses that temporarily reshape the central cornea to correct refractive error, enabling emmetropic vision during the day without optical aids.[176] This method, introduced in the 1960s but refined for myopia management in recent decades, induces peripheral defocus to modulate retinal signals that influence eye growth, thereby slowing axial elongation in myopic children.[145] Randomized controlled trials and meta-analyses indicate that orthokeratology reduces myopia progression by approximately 45-50% compared to single-vision spectacle wear over the first year, with axial length growth slowed by 0.15-0.25 mm annually in treated groups versus 0.30 mm in controls.[177][178] Longitudinal studies demonstrate sustained but diminishing efficacy beyond two years, with progression control rates dropping to 30-40% relative to untreated peers, potentially due to central corneal flattening limits and patient compliance issues.[179] A 2023 meta-analysis of randomized trials confirmed orthokeratology's superiority over soft contact lenses for axial length control in children aged 6-12, though effects vary by baseline myopia severity and lens fit quality, with greater benefits observed in low to moderate myopes (-1.00 to -4.00 diopters).[180] Safety profiles are favorable, with microbial keratitis incidence at 7.7 per 10,000 patient-years when hygiene protocols are followed, comparable to daily disposable contacts, but dropout rates reach 20-30% due to discomfort or handling errors.[176] Emerging optical interventions build on orthokeratology principles by incorporating advanced defocus mechanisms. Repeated low-level red-light (RLRL) therapy (650 nm, typically 3 minutes twice daily, 5 days/week, delivered via desktop devices) has demonstrated significant slowing of myopia progression in randomized trials and meta-analyses, primarily in children. It reduces axial length elongation by approximately 0.20-0.30 mm over 12 months compared to controls, with associated choroidal thickening and, in some cases, axial shortening (average -0.11 mm in high myopes after one year, with shortening in 53-59% of cases). Studies report refraction improvements up to 1D in real-world cases, positioning RLRL as the closest current approach to partial reversal via axial shortening, while most treatments primarily slow progression. Meta-analyses confirm efficacy in delaying progression and potentially onset in pre-myopia, though rebound after cessation is a concern. Long-term (up to 3-year) real-world data show sustained benefits with good safety in compliant users, but US evaluations highlight risks of retinal photochemical and thermal damage from certain devices exceeding ANSI safety limits, with some studies noting reduced paracentral cone density. Approved RLRL devices in some countries include mandatory safety features such as auto shut-off, distance sensors, usage tracking and child lockout features. More global studies are needed to fully establish long-term safety and efficacy.[181][182][183][184][185][186] Dual-focus or peripheral defocus spectacle lenses, such as defocus-incorporated multiple segments, achieve 50-60% reduction in progression in randomized trials, offering a non-invasive alternative suitable for younger children averse to contacts.[145] Combination approaches, integrating orthokeratology with low-concentration atropine, yield additive effects, slowing progression by up to 70% in 2-year studies, though regulatory approvals and cost barriers limit widespread adoption as of 2025.[187] These methods prioritize causal modulation of emmetropization signals over mere correction, with ongoing trials assessing genetic and environmental modifiers for personalized efficacy.[142]

Historical Perspectives

Pre-Modern Observations

The earliest recorded observation of myopia dates to Aristotle in approximately 350 BC, who coined the term myops (from the Greek myein, meaning "to close" or "squint," and ops, meaning "eye") to describe individuals who could see nearby objects clearly but struggled with distant vision, often squinting, blinking frequently, and exhibiting protruding eyes, which he attributed to excessive near work like reading.[188] In ancient Rome, Emperor Nero (reigned AD 54–68) exhibited severe myopia, reportedly employing a concave-cut emerald held to his eye as a primitive corrective lens to better observe gladiatorial combats from afar.[188] Galen of Pergamon (AD 129–c. 216) further elaborated on the condition in his medical writings, emphasizing the squinting behavior as a diagnostic feature and distinguishing it from other visual defects.[189] Byzantine physician Aetius of Amida (fl. AD 502–567) referred to myopia as lusciositas in his encyclopedic work Tetrabiblos, noting its association with blurred distant vision and recommending environmental adjustments rather than optical aids.[188] Medieval Islamic scholars, including Ibn al-Haytham (Alhazen, 965–1040), advanced optical understanding through experiments on refraction and vision, indirectly informing myopia by demonstrating how light rays converge improperly in the eye, though they did not explicitly diagnose the condition's prevalence.[189] In the early modern period preceding widespread spectacle use, Hermann Boerhaave (1668–1738) hypothesized in 1720 that myopia resulted from elongated eye globes, potentially caused by infections, tumors, or developmental factors, marking an early causal insight based on anatomical dissection rather than mere symptomatic description.[188] These pre-modern accounts, drawn primarily from Greco-Roman and Byzantine texts, highlight myopia as a recognized but unmanaged defect, often linked anecdotally to scholarly pursuits, with no effective interventions until the invention of concave lenses around 1286.[188][189]

Modern Etiological Insights

The recognition of myopia as a condition influenced by both genetic and environmental factors solidified in the mid-20th century, building on earlier observations of familial clustering. Twin and family studies conducted from the 1960s to 1990s estimated heritability of myopia at 60-90%, indicating a substantial genetic component, yet the heritability figures failed to account for rapid prevalence increases within single generations, pointing to non-genetic triggers.[59][56] Epidemiological data from the late 20th century highlighted environmental correlates, including urbanization and educational intensity, with studies in East Asia showing myopia rates exceeding 80% among urban high school students by the 1990s, compared to under 20% in rural counterparts.[190] Prolonged near work—intensive close-focus activities like reading—was implicated as a risk factor, with meta-analyses linking each additional diopter-hour of near work per week to a 2% increased odds of myopia onset in children.[65] However, causal mechanisms remained debated, as cross-sectional associations did not consistently hold in longitudinal designs, suggesting near work acts primarily in genetically susceptible individuals.[191] A transformative insight emerged around 2005 from Australian and Asian cohort studies: time spent outdoors inversely correlates with myopia development, independent of near work levels. Randomized school-based interventions, such as adding 80 minutes of daily outdoor recess, reduced new myopia cases by 50% over one year in Taiwanese children aged 6-7.[51] Meta-analyses of 25 studies confirmed that each additional hour of outdoor exposure per day lowers myopia risk by 2-13%, with effects strongest before age 12 when emmetropization occurs.[190][192] Mechanistically, bright natural light (10,000-100,000 lux outdoors versus 100-500 lux indoors) is proposed to elevate retinal dopamine levels, suppressing scleral extracellular matrix remodeling that drives axial elongation—the primary structural change in myopic eyes.[145] Animal models support this, showing dopamine agonists prevent form-deprivation myopia, while human trials link sunlight intensity, not mere outdoor presence, to protection via smartwatch-measured exposure data.[53] Gene-environment interactions amplify these effects; variants in dopamine-related genes modulate outdoor time's protective role.[56] The COVID-19 pandemic (2020-2022) provided quasi-experimental evidence, with lockdowns correlating to a 1.5-2 times faster myopia progression in children due to reduced outdoor activity (from 2 hours/day to under 1) and heightened screen time exceeding 3 hours/day.[193] These findings underscore environmental dominance in the modern myopia epidemic, where prevalence among young adults in industrialized regions rose from 20-30% in the 1970s to 40-50% by 2020, necessitating public health interventions focused on light exposure over genetics alone.[194]

Contemporary Research Advances

Recent epidemiological studies project that myopia will affect 39.8% of the global population by 2050, with higher rates in East Asia and among children in low- and middle-income countries, driven by environmental factors including reduced outdoor exposure.[195][196] In Asia, prevalence among 15-19-year-olds in China reached 68.9% as of 2024, underscoring the ongoing epidemic's severity.[197] Randomized controlled trials have strengthened evidence for increased outdoor time as a preventive measure, with school-based interventions adding 40 minutes daily reducing myopia incidence by up to 23% and myopic shifts, particularly in non-myopic children, through mechanisms potentially involving higher light intensity exposure.[198][199] A 2025 cluster-randomized trial further demonstrated that outdoor scene classrooms, enhancing natural light access, arrested myopia progression in participants compared to standard indoor settings.[200] Pharmacological advances center on low-dose atropine eye drops, with meta-analyses of randomized trials confirming 0.01% atropine reduces myopia progression and axial elongation by 30-50% over 2-3 years versus placebo, with minimal side effects like photophobia.[159][156] The International Myopia Institute's 2025 report highlights over 70% of recent clinical trials focusing on such interventions, noting consistent efficacy across concentrations from 0.01% to 0.05%, though rebound effects post-treatment warrant long-term monitoring.[142] Optical strategies have progressed with defocus-incorporated spectacles and multifocal contact lenses modulating retinal defocus to slow axial elongation by 20-60% in trials, outperforming single-vision lenses.[145] Orthokeratology, involving overnight rigid lens wear, showed sustained myopia control over three years in a 2025 longitudinal study of 1,303 children, reducing progression by 40-50%.[201] Emerging research explores novel targets like adenosine receptor antagonists and vitamin D supplementation, with preclinical data suggesting roles in scleral remodeling, though human trials remain preliminary as of 2025.[202] The 2025 World Society of Paediatric Ophthalmology and Strabismus consensus emphasizes combining behavioral, optical, and pharmacological approaches for multifactorial control, prioritizing high-risk populations.[203]

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