Myopia: An epidemic of global proportions

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Many current articles on myopia contain a citation to the 2016 study by Holden et al, which discusses the increasing prevalence of myopia worldwide.¹ At the time of the study, approximately 23% of the world’s population had myopia, with a predicted increase to 50% by the year 2050. The highest prevalence rates were found in Asia-Pacific countries, with East Asia, Southeast Asia, and North America not far behind.¹ This meta-analysis confirmed that the prevalence of myopia was high and would continue to increase if no corrections were introduced; however, traditional corrections were proving ineffective. The rising concern surrounding this myopia epidemic is related to the numerous consequences of high myopia, including vision impairment, economic burden, and decreased quality of life (QOL).

Myopia development

Myopia is a mismatch between the ocular power of the eye and the axial length, resulting in blurred distance vision.² The typical onset of myopia occurs in children aged 6 to 9 years.³ This is considered juvenile-onset or school-age myopia, which is different from pathological myopia, a condition characterized by excessive axial elongation resulting in structural changes to the posterior segment of the eye.² The earlier the age of onset, the more at risk an individual is for developing high myopia because there is a longer period for myopia to progress.⁴

The level of hyperopia that a child has at a certain age can be a risk factor for developing myopia. At 6 years of age, a child should have a refractive error of +0.75 D or greater; any less and they are more likely to develop myopia.⁵ Additionally, individuals with myopia show faster axial elongation in the 2 to 3 years preceding myopia onset.⁶

Genetic, environmental, and lifestyle factors for myopia development have been identified. Parental myopia increases the risk of myopia development; having 1 myopic parent increases a child’s likelihood by a factor of 3, and having 2 myopic parents increases the likelihood by a factor of 5-6.⁷ However, genomewide association studies are only able to account for 8% of the phenotypic variation.⁸ With the rapid increase in the prevalence of myopia and the limited genetic variability over the same period, it is more likely that environmental and behavioral factors are responsible for myopia development. Specifically, strong evidence supports that time outdoors, light intensity, and near work all play a role in reducing myopia development and progression.⁹ Increasing time spent outdoors is thought to delay myopia onset because it is associated with reduced myopia prevalence.¹⁰ The recommendation is 2 hours per day or 10 hours per week.¹¹ Additionally, increasing near working distance and the number of breaks in continuous near work is associated with reduced risk of myopia.¹²

Vision impairment

The fight against myopia is propelled by the concern of potential long-term ocular complications. Individuals with myopia are at an increased risk of cataracts, glaucoma, myopic macular degeneration, and retinal detachment.¹³ All of these complications are a result of the eye growing longer, which causes the retina and choroid to thin. Myopic maculopathy is the most characteristic complication and results in vision loss due to atrophy of the retinal pigment epithelium.¹⁴ It is one of the most common causes of visual impairment among individuals with myopia.⁴ As myopia progresses and axial length continues to increase, the risk for visual impairment increases. Tideman et al found that an axial length of 26 mm or greater is significantly associated with an increased lifetime risk for visual impairment.¹⁵

The risk for these ocular diseases increases with increasing levels of myopia; however, there is no safe level of myopia. For each diopter increase in myopia, the risk of myopic maculopathy increases by 67%. However, slowing myopia by 1 diopter reduces the likelihood of developing myopic maculopathy by 40%.¹⁶ Therefore, the practitioner’s primary goal should be to delay the onset of myopia. Once myopia develops, interventions should be implemented to slow myopia progression.

Economic burden

Uncorrected refractive error is the second leading cause of blindness worldwide and the leading cause of moderate and severe vision impairment.¹⁷ Thus the economic burden of myopia is significant, resulting in direct costs (eg, diagnosis, treatment, and management of the condition) and productivity loss (eg, examination time, time away from work or home).¹⁸

The earlier a child develops myopia and the longer they have the condition, the greater the total economic burden is. The cost associated with examinations and materials varies between countries and even between regions. In systematic review data from 2015, researchers found the global potential productivity loss was $244 billion from uncorrected myopia and $6 billion from myopic maculopathy.¹⁹ Older individuals with myopia and those who live in rural areas were less likely to have adequate optical correction. On a global scale, East Asia is the hardest-hit region in terms of greatest potential burden. Naidoo et al concluded that the potential productivity loss from vision impairment by uncorrected myopia was significantly greater than the cost of correcting myopia.¹⁹

The cost of active myopia management therapies has been compared with the traditional methods of myopia correction. Agyekum et al found that in Hong Kong atropine had a cost-effectiveness ratio of $220 per spherical equivalent refractive error reduction, whereas outdoor activity saved $5 per spherical equivalent reduction.²⁰ The lifetime cost of traditional myopia correction in China was $8006, compared with antimyopia spectacles ($7280) and low-dose atropine ($4453). Therefore, active myopia management therapies are of equal or lesser cost compared with traditional correction of myopia alone.²¹

Orthokeratology lenses

Patient-reported outcomes are becoming more salient because these myopia interventions are being used specifically for children. Although children can adapt readily, they also may not voice their concerns or understand what is normal or abnormal.

In a recent review on myopia management interventions and their effect on vision-related QOL, Lipson et al found that QOL was higher for children wearing orthokeratology lenses compared with those wearing single-vision spectacles or single-vision soft contact lenses.²² Additionally, contact lenses have been shown to improve children’s self-perception compared with spectacles in terms of physical appearance, athletic competence, and social acceptance.²³

Myopia management

Myopia is a global epidemic and a public health concern. Eye care providers should be implementing myopia management therapies as the standard of care for all children with myopia and potentially those with premyopia. The basis of this clinical practice is to shift perspective and view myopia as a sight-threatening disease rather than a simple refractive error. Practitioners must educate patients and parents on the short- and long-term consequences of myopia and the current options to slow myopia progression, including spectacle lenses, low-dose atropine, soft peripheral defocus contact lenses, and orthokeratology lenses. As the prevalence of myopia continues to rise, these therapies should be implemented to combat the vision impairment, economic burden, and decreased quality of life associated with myopia.

References

1. Holden BA, Fricke TR, Wilson DA, et al. Global prevalence of myopia and high myopia and temporal trends from 2000 through 2050. Ophthalmology. 2016;123(5):1036-1042. doi:10.1016/j.ophtha.2016.01.006

2. Flitcroft DI, He M, Jonas JB, et al. IMI – defining and classifying myopia: a proposed set of standards for clinical and epidemiologic studies. Invest Ophthalmol Vis Sci. 2019;60(3):M20-M30. doi:10.1167/iovs18-25957

3. McCullough SJ, O’Donoghue L, Saunders KJ. Six year refractive change among white children and young adults: evidence for significant increase in myopia among white UK children. PLoS One. 2016;11(1):e0146332. doi:10.1371/journal.pone.0146332

4. Holden B, Sankaridurg P, Smith E, Aller T, Jong M, He M. Myopia, an underrated global challenge to vision: where the current data takes us on myopia control. Eye (Lond). 2014;28(2):142-146. doi:10.1038/eye.2013.256

5. Zadnik K, Sinnott LT, Cotter SA, et al; Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) Study Group. Prediction of juvenile-onset myopia. JAMA Ophthalmol. 2015;133(6):683-689. doi:10.1001/jamaophthalmol.2015.0471

6. Mutti DO, Hayes JR, Mitchell GL, et al. Refractive error, axial length, and relative peripheral refractive error before and after the onset of myopia. Invest Ophthalmol Vis Sci. 2007;48(6):2510-2519. doi:10.1167/iovs06-0562

7. Mutti DO, Mitchell GL, Moeschberger ML, Jones LA, Zadnik K. Parental myopia, near work, school achievement, and children’s refractive error. Invest Ophthalmol Vis Sci. 2002;43(12):3633-3640.

8. Tedja MS, Haarman AEG, Meester-Smoor MA, et al. IMI – myopia genetics report. Invest Ophthalmol Vis Sci. 2019;60(3):M89-M105. doi:10.1167/iovs18-25965

9. Biswas S, El Kareh A, Qureshi M, et al. The influence of the environment and lifestyle on myopia. J Physiol Anthropol. 2024;43(1):7. doi:10.1186/s40101-024-00354-7

10. Rose KA, Morgan IG, Ip J, et al. Outdoor activity reduces the prevalence of myopia in children. Ophthalmology. 2008;115(8):1279-1285. doi:10.1016/j.ophtha.2007.12.019

11. Xiong S, Sankaridurg P, Naduvilath T, et al. Time spent in outdoor activities in relation to myopia prevention and control: a meta-analysis and systematic review. Acta Ophthalmol. 2017;95(6):551-566. doi:10.1111/aos.13403

12. Ip JM, Saw SM, Rose KA, et al. Role of near work in myopia: findings in a sample of Australian school children. Invest Ophthalmol Vis Sci. 2008;49(7):2903-2910. doi:10.1167/iovs07-0804

13. Flitcroft DI. The complex interactions of retinal, optical and environmental factors in myopia aetiology. Prog Retin Eye Res. 2012;31(6):622-660. doi:10.1016/j.preteyeres.2012.06.004

14. Hayashi K, Ohno-Matsui K, Shimada N, et al. Long-term pattern of progression of myopic maculopathy: a natural history study. Ophthalmology. 2010;117(8):1595-1611. doi:10.1016/j.ophtha.2009.11.003

15. Tideman JWL, Snabel MCC, Tedja MS, et al. Association of axial length with risk of uncorrectable visual impairment for Europeans with myopia. JAMA Ophthalmol. 2016;134(12):1355-1363. doi:10.1001/jamaophthalmol.2016.4009

16. Bullimore MA, Brennan NA. Myopia control: why each diopter matters. Optom Vis Sci. 2019;96(6):463-465. doi:10.1097/OPX.0000000000001367

17. Bourne RRA, Stevens GA, White RA, et al; Vision Loss Expert Group. Causes of vision loss worldwide, 1990-2010: a systematic analysis. Lancet Glob Health. 2013;1(6):e339-e349. doi:10.1016/S2214-109X(13)70113-X

18. Sankaridurg P, Tahhan N, Kandel H, et al. IMI impact of myopia. Invest Ophthalmol Vis Sci. 2021;62(5):2. doi:10.1167/iovs62.5.2

19. Naidoo KS, Fricke TR, Frick KD, et al. Potential lost productivity resulting from the global burden of myopia: systematic review, meta-analysis, and modeling. Ophthalmology. 2019;126(3):338-346. doi:10.1016/j.ophtha.2018.10.029

20. Agyekum S, Chan PP, Adjei PE, et al. Cost-effectiveness analysis of myopia progression interventions in children. JAMA Netw Open. 2023;6(11):e2340986. doi:10.1001/jamanetworkopen.2023.40986

21. Fricke TR, Sankaridurg P, Naduvilath T, et al. Establishing a method to estimate the effect of antimyopia management options on lifetime cost of myopia. Br Journal Ophthalmol. 2022;107(8):1043-1050. doi:10.1136/bjophthalmol-2021-320318

22. Lipson MJ, Boland B, McAlinden C. Vision-related quality of life with myopia management: a review. Cont Lens Anterior Eye. 2022;45(3):101538. doi:10.1016/j.clae.2021.101538

23. Walline JJ, Jones LA, Sinnott L, et al; ACHIEVE Study Group. Randomized trial of the effect of contact lens wear on self-perception in children. Optom Vis Sci. 2009;86(3):222-232. doi:10.1097/OPX.0b013e3181971985