The Fundamentals of Myopia

Experts forecast that by 2050 half of the world’s population will be myopic. But what’s more concerning is that the proportion of myopes that are likely to become high myopes will be nearly ten percent in 2050.¹ In many parts of Asia, these figures are already a reality. In a study that considered two million 18-year-olds the prevalence of high myopia rose from 14 percent in 2014 to 18 percent in 2018.² In light of these staggering figures, we’ve asked Prof Padmaja Sankaridurg some pressing questions about the increasing prevalence of myopia.

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What we observe is a rising trend in myopia prevalence.

Prof Padmaja Sankaridurg Head of Global Myopia Management, ZEISS Vision Care | Chair of the ZEISS Myopia Advisory Board

Figure 2: The grey bars represent numbers from 2010 and the blue bars from 2020. Across all levels of myopia the number of prescriptions that are devoted to higher levels of myopia increased. | Source: Carnerio VL, Gonzalez Meijome JM. PLOS One 18(4), 2023.

Myopia and the increase in the number of high myopes seems to be prevalent in Asia. Is it also a problem in the rest of the world?

Indeed, the prevalence of myopia in Europe and other parts of the word is lower than in Asia. Despite this variation in prevalence, overall, the prevalence is rising in many parts of the world. A study conducted in Portugal, considered all spectacle lens prescriptions from a leading lens manufacturer and the proportion of prescriptions that were myopic. In just over a decade, the period from 2010 to 2020, the myopic prescriptions rose from 40.9 to 50.7 percent.³ This is indicative of the increase in myopia. This study also shows that an increasing number of prescriptions are made for higher levels of myopia, and this is quite significant (Figure 2). A recent study from Olmsted Country, Minnesota, USA also registered an increase in prevalence of myopia and high myopia from 33.9 percent and 2.8 percent in 1960s to 57.1 percent and 8.3 percent in 2010.⁴ Although this data appears to be based on non-cycloplegic refraction, what we observe is a rising trend in myopia prevalence.

Figure 3: Source: Ma Y, Qu X, Zhu X, Xu X, Zhu J, Sankaridurg P, et al. Invest Ophthalmol Vis Sci. 2016;57(14):6188-6196.

Why is the prevalence of high myopia increasing?

Two important observations point to the reason as to why the prevalence of high myopia is increasing. The first is the age of myopia onset. If we look at data from Asian countries (lot more published evidence from this region), five to 18 percent of children as young as four to six years are already myopic. At six years of age there is a dramatic increase in the prevalence of myopia and by ten years, more than 30 percent of the children are myopic (Figure 3).⁵ A child who becomes myopic at a very young age is likely to spend many years in the progression phase and reach higher levels of myopia.

Figure 4: Progression is greater at younger ages. Therefore, net myopia for an individual with early onset is greater. | Source: Chua SY, Sabanayagam C, Cheung YB, Chia A, Valenzuela RK, et al. Opo 2016;36(4):388-94.

Secondly, we have what we call an age-related progression. Annual progression of myopia is faster in younger children. The annual myopia progression of a six-year-old is nearly twice that of an eleven-year-old. Therefore, a child with early onset of myopia progresses faster and spends more years in the progression phase and therefore, likely to reach higher levels of myopia. For example, a child with myopia onset at six years is nearly highly myopic at eleven years compared to a child who has onset at nine years of age (Figure 4).

What impact does it have on the individual and society?

The impact of myopia is multifold. Firstly, myopia results in vision impairment. At higher levels and especially in older individuals, myopia increases the risk of pathological complications such as myopic macular degeneration, retinal detachment, open angle glaucoma or cataracts. It is estimated there will be a fivefold increase in the number of eyes experiencing severe visual impairment due to myopic macular degeneration by the year 2050.⁶

Myopia imposes a significant financial burden for the individual and their family. The “direct costs” for a person with myopia include expenses associated with optical devices such as spectacles or contact lenses; examinations and treatments. At higher levels of myopia, there may be costs for specialist services such as treatments due to complications. In comparing the lifetime costs for example for a -0.75D myope with onset at eight years of age, living in Australia versus China, whilst the costs for services and goods were lower in China than in Australia, a person in China is going to end up with higher lifetime costs because he or she is more likely to have higher levels of myopia compared to Australia. The myope in China will have more frequent follow-ups, more changes of optical devices and so on. The reality is, with each increasing diopter the lifetime cost burden is going to be substantial for the affected person.⁷

Another important consequence is the economic impact. For urban China for 2016, alone the figures were equivalent to 0.3 of GDP. Data shows that the biggest area of impact is the loss of productivity due to moderate to severe vision impairment and blindness resulting from myopia amounting to a whopping 16.1 billion USD.⁸

How does this influence the practice of eye care professionals?

Myopia is going influence the way they practice in the future. Whilst presently, there is more focus on the younger myope, in years to come there will be more myopes- both younger and older attending the practice. The practice model needs to adapt to the age dependent needs. The younger myopes will require active myopia management and management of the progression. This means there will be more frequent follow-ups. For the older myopic individuals, presbyopia management becomes central. The risks of complications also have to be kept in mind for those with higher levels of myopia.

How do we manage this development of myopia?

The most effective approach would be to try and prevent or delay the onset of myopia. More time spent outdoors with emphasis on light exposure is useful. In already myopic individuals, it’s very important for myopia management to be practiced actively. Changing the trajectory of the rising impact of myopia involves multiple stakeholders such as the family, community, the individual themselves and the practitioners. Additionally, the industry has an important role in providing the most suitable products and to equip the practitioners with the best tools. Presently, there are multiple options such spectacle lenses, contact lenses, and ortho-k and pharmaceutical options that are available to slow myopia.

Of these options, spectacles are a convenient option especially for the young myope. The more effective newer generations of spectacle lenses incorporate a clear central zone that corrects for the refractive error of the eye and a treatment zone in the periphery. The treatment zone incorporates multiple segments, elements or microstructures that are aimed to deliver simultaneous myopic defocus at the retina or reduce peripheral hyperopic defocus.

ZEISS has different products to manage progression in the myope including the recent MyoCare lenses. ZEISS MyoCare lens incorporates Cylindrical Annual Refractive Elements that are placed in the treatment zone, are relatively more positive in power and alternate with clear zones that correct for distance error. The annular elements in conjunction with the clear zones deliver simultaneous myopic defocus at the retina. Data indicates that use of these lenses slow myopia.

¹
Holden, Fricke, Wilson, Jong, Naidoo, Sankaridurg et al. Ophthalmology, 2016 123(5):1036-42.
²
Gwon SH, Lee DC. Factors associated with myopia in 19-year-old adult men in Korea between 2014 and 2020. Sci Rep. 2023 Jul 18;13(1):11581.
³
Carnerio VL, Gonzalez Meijome JM. PLOS One 18(4, 2023.
⁴
Tailor PD, Xu TT, Tailor S, Asheim C, Olsen TW. Trends in Myopia and High Myopia from 1966 to 2019 in Olmsted County, Minnesota. Am J Ophthalmol. 2024 Mar;259:35-44.
⁵
Ma Y, Qu X, Zhu X, Xu X, Zhu J, Sankaridurg P, et al. Invest Ophthalmol Vis Sci. 2016;57(14):6188-6196.
⁶
Fricke TR, Jong M, Naidoo KS et al . Br J Ophthalmol, 102(7), 855 2018
⁷
Fricke TR, Sankaridurg P, Naduvilath T, Resnikoff S, Tahhan N, He M, Frick KD. Establishing a method to estimate the effect of antimyopia management options on lifetime cost of myopia. Br J Ophthalmol. 2023 Aug;107(8):1043-1050
⁸
Ma Y, Wen Y, Zhong H, et al. J Glob Health. 2022 Mar 19;12:11003