In recent times, the issue of myopia has featured heavily in mainstream media with headlines such as “the myopia boom”[1] and “night time contact lenses stop children becoming short-sighted.”[2] The growing concern surrounding myopia has already led to governments in some parts of the world taking measures to ameliorate this problem. In Taiwan, a law was passed “banning too much screen time,” and public health campaigns in Singapore encouraged children to spend more time outdoors. Given these messages, we may be left wondering about the size of the burden of myopia, and the strategies and/or solutions required to reduce it. 

The size of the problem

Recent work from the Brien Holden Vision Institute estimates that the prevalence of myopia (≤ -0.50 D) will increase world-wide, from 28% (2 billion) of the global population in 2010, to nearly 50% (5 billion) of the world population by 2050. As a consequence, the prevalence of high myopia (≤ -5.00D) is also likely to increase from 4% (277 million) in 2010, to nearly 10% (1 billion) by the year 2050.[3] Figure 1 illustrates the prevalence of myopia and high myopia from 2000 through to 2050.

 
Fig. 1: The estimated global prevalence of myopia and high myopia per decade from 2000 to 2050 based on current trends.  The number of people in millions is listed on the y-axes.  Adapted from Holden et al.[3]

The shift towards myopia

The shift towards myopia has been rapid in some parts of the world, such as the USA where the prevalence of myopia increased from 26% to 42% from 1972 to 2004.[4] In Singapore, the prevalence of myopia was 47% in adults in their 20s, and 26% in adults in their 50s.[5] 

High myopia (≤ - 7.90 D) in the USA has already increased 8-fold over 30 years from 0.2% to 1.6%.[4] In 18 year old Taiwanese students, 21.0% had high myopia (≤ -6.00 D) in 2000 compared with 10.9% in 1983.[6] Globally in 2000, most people with myopia were below age 40, and little myopia was seen in those over 40. By 2030, the prevalence of myopia is approximately 50% for all age groups above 20 years, and by 2050, it is up to 68%[7] (Figure 2). Regions with traditionally little myopia, such as Eastern Europe and Southern Africa will also see a large shift towards myopia in the near future, approaching prevalences of 50% and 30% by 2050 and is likely due to lifestyle changes as a result of urbanisation and development (Figure 3).[3] 

Fig. 2: The global generational shift in myopia indicates that in the earlier decades of 2000 up to 2030, the majority of myopia is occurring in those under forty years with little myopia seen in those over forty. After 2030, the prevalence of myopia is affecting all age groups.  Adapted from Holden et al.[3]

Fig. 3: The increasing prevalence of myopia estimated across the world from the year 2000 to 2050.  Modified from Holden et al. 2016.[3]
 

What are the consequences?

The economic burden of uncorrected distance refractive error was estimated to be US$202 billion per annum, of which myopia is the main cause.

Uncorrected refractive error is the leading cause of distance vision impairment globally, affecting 108 million people, and is the second most common cause of global blindness.[8] The economic burden of uncorrected distance refractive error was estimated to be US$202 billion per annum, of which myopia is the main cause.[9] With the rising prevalence of myopia, the economic burden of uncorrected refractive error associated with myopia will rise. In addition, myopia is associated with ocular complications such as myopic macular degeneration, retinal detachment, cataract and glaucoma which impose a significant health and economic burden. Myopic macular degeneration is already a frequent cause of vision impairment in Japan,[10] China,[11] Netherlands [12] and Denmark.[13] It is important to note that any level of myopia increases the risks of the above mentioned problems compared to emmetropes, but the risk increases exponentially once you reach high myopia.14 For myopia of -5.00 D to -7.00 D, the risk of glaucoma is 3.3 times, the risk of cataract is 5.5 times, the risk of retinal detachment is 21.5 times, and the risk of myopic macular degeneration is 40.6 times.[14] The future estimates of myopia, suggest that at least one billion people are potentially at risk of developing permanent vision impairment and blindness associated with high myopia.[15]

The future estimates of myopia, suggest that at least one billion people are potentially at risk of developing permanent vision impairment and blindness associated with high myopia

Strategies to manage the burden 

Both environmental and genetic factors are thought to contribute to the onset and progression of myopia, but it has been suggested that environmental factors have a larger role to play in the rapid increase in the prevalence of myopia. A heavily indoor and near-activity based lifestyle,[16, 17] with less time outdoors,[18] combined with the intense education commencing at very young ages, as occurring in many East Asian countries, are major contributing factors.[16] 

Evidence is now growing to support the use of interventions in slowing myopia progression. Optical interventions that modulate the visual feedback and environmental interventions promoting increased outdoor time can successfully delay and slow the progress of myopia in an individual. Optical strategies shown to slow the progress of myopia include ortho-K (30% to 57%),[19, 20] multifocal-type soft contact lenses (25% to 72%),[20] and executive bifocals (39% to 51%).[21] Progressive addition spectacles are limited to 15% to 20%.[21] Time outdoors has successfully reduced the number of new cases of myopia by up to 50%, and can effectively delay the onset of myopia, but its ability to slow the rate of progression of myopia is not clinically significant.[22, 23] In addition, certain pharmaceutical approaches have also shown promise, with low dose atropine (0.01%) slowing the progress of myopia by almost 59%.[24] The long term effects of atropine use are not yet clear.

Future needs

An effective myopia management strategy that combines the individual’s need, based on their risk profile (for example, age, lifestyle, familial history), and matched to the appropriate intervention strategy is required, to reduce the burden of myopia, both at the individual, and the community level. Recognising the need, the World Health Organisation (WHO) convened a Global Scientific Meeting on Myopia, in collaboration with the Brien Holden Vision Institute in Sydney, Australia in 2015. At this forum, leading experts in myopia met to examine the latest evidence, identify gaps in knowledge, and define policies for the management of myopia. It is expected that this report will be published soon, and will provide myopia management guidelines for governments, industry, health care workers, and practitioners.

Conclusion

The projected increases in myopia, and high myopia affecting almost 5 billion and 1 billion people, respectively, by 2050 have important implications for planning comprehensive eye care services, including refractive services such as spectacles and contact lenses for correcting and slowing myopia progression, as well as preventing and managing high myopia related ocular complications. The optical industry also has a key role to play in education, developing, and supporting appropriate myopia management strategies to help reduce the burden of myopia. • 

More information
For further details, “Global Prevalence of Myopia and High Myopia and Temporal Trends from 2000 through 2050” is available via open access at http://www.sciencedirect.com/science/article/pii/S0161642016000257.