What is myopia?

What is myopia?

Myopia is a condition where near objects are clearly visible, but distant objects appear blurry and hard to see. In a normal state (emmetropia), where one can see objects clearly at all distances, the focus is on the retina. However, in myopia, the focus is in front of the retina.

There are various types of myopia, but most are referred to as ‘axial myopia,’ which occurs due to an increase in near work activities, causing the axial length of the eye to elongate.

Good Practices for Myopia Prevention

Outdoor activities are said to be beneficial for the eyes, with numerous studies reporting that they help suppress the onset and delay the progression of myopia.
Outdoor activities naturally allow the eyes to focus on distant objects, easing the strain caused by near work activities.
It has also been found that children who are exposed to outdoor light, which can only be reproduced outdoors, for more than 11 hours a week are less likely to develop myopia.
On the other hand, modern life, with the widespread use of digital content, has led to increased indoor play and, along with various social factors, a decrease in our outdoor activities year by year.

Outdoor
Activity Time and Myopia

The longer the time spent outdoors, the lower the incidence of myopia, and it may also be correlated with a slower progression of myopia.
If outdoor activities are less than 13 hours a week (about 2 hours a day), the risk of myopia significantly increases (*1).

Protecting the Ability to See Distant Objects

Even among hunter-gatherer societies, data shows that people living in urban areas experience a decline in vision to an average of around 1.0, suggesting that the living environment plays a role.

Myopia: The Most Common Lifestyle Disease

2,620

Myopia

1,900

Obesity

1,795

Hyperlipidemia

1,560

Hypertension

465

Diabetes

389

Arthritis

(Unit: per million)

Forecast of Lifestyle Disease Patients

Currently, myopia is one of the most common diseases, with a large number of patients among lifestyle diseases. The global prevalence of myopia is increasing, and according to the World Health Organization (WHO), it is predicted that 50% of people will have myopia by 2050. Additionally, the proportion of people with high myopia is also expected to increase (*2).

In particular, the myopia population in Asia has significantly increased, with the prevalence of myopia in adults being 30-40% in Europe and America, compared to 80% in Asia.

Even compared to 20 years ago, the prevalence of myopia in children has dramatically increased, and it is estimated to continue rising.

The Risks of Myopia

If the axial length of the eye excessively elongates, leading to high myopia, it can result in severe visual impairments such as glaucoma, cataracts, retinal detachment, or retinal separation. The more myopia progresses, the higher the risk of these diseases, and particularly if high myopia develops in childhood, the risk is further increased.

(In case of -5D)

Retinal Detachment

40.6

Times more likely

Cataracts

3.1

Times more likely

Glaucoma

3.3

Times more likely

If the axial length of the eye excessively elongates, leading to high myopia, it can result in severe visual impairments such as glaucoma, cataracts, retinal detachment, or retinal separation. The more myopia progresses, the higher the risk of these diseases, and particularly if high myopia develops in childhood, the risk is further increased.

The Mechanism of Myopia

Myopia is classified into refractive myopia, axial myopia, and pseudo-myopia, but most cases are referred to as axial myopia.

Axial myopia is a phenomenon where the axial length of the eye elongates in an elliptical shape, causing the focus to be off the retina.

Factors in the Onset of Myopia

Myopia occurs when the axial length of the eye (the distance from the cornea to the retina) is longer than normal or when the refractive power of the cornea or lens is too strong. The eyeball elongates as children grow, but typically, it is said to stop growing between the ages of 10 and 12. The causes of myopia are believed to be environmental factors, such as increased near work, and genetic factors. If both parents are myopic, their children are more likely to develop myopia. However, the rapid increase in myopia cases in recent years cannot be explained solely by genetic factors, and it is believed that environmental factors and other factors play a stronger role.

Decrease in Outdoor Activities

Excessive Use of Digital Devices

Various Activities That Strain the Eyes

Sources:
*1Xiong S, Sankaridurg P, Naduvilath T, Zang J, ZWu PC, Chen CT, Lin KK, Sun CC, Kuo CN, Huang HM, Poon YC, Yang ML, Chen CY, Huang JC, Wu PC, Yang IH, Yu HJ, Fang PC, Tsai CL, Chiou ST, Yang YH. Myopia Prevention and Outdoor Light Intensity in a School-Based Cluster Randomized Trial. Ophthalmology. 2018 Aug;125(8):1239-1250. doi: 10.1016/j.ophtha.2017.12.011. Epub 2018 Jan 19. PMID: 29371008.
Zou H, Zhu J, Lv M, He X, Xu X. Time spent in outdoor activities in relation to myopia prevention and control: a meta-analysis and systematic review. Acta Ophthalmol. 2017 Sep;95(6):551-566.

*2Myopia: Holden BA et al. Global prevalence of myopia and high myopia and temporal trends from 2000 through 2050. Ophthalmology. 2016;123(5):1036–1042 International Myopia Institute
https://www.myopiainstitute.org/prevalence.html Obesity: World Health Organization. https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight Hyperlipidemia: World Health Organization.
https://www.who.int/gho/ncd/risk_factors/cholesterol_prevalence/en/ Hypertension: Mills KT et al. Global Disparities of Hypertension Prevalence and Control: A Systematic Analysis of Population-Based Studies From
90 Countries. Circulation. 2016;134(6):441‐450 Diabetes: Saeedi P et al. Global and regional diabetes prevalence estimates for 2019 and projections for 2030 and 2045: Results from the International Diabetes
Federation Diabetes Atlas, 9th edition. Diabetes Res Clin Pract. 2019;157:107843 Arthritis: Osteoarthritis Research Society International