Is myopia hereditary?

June 6, 2022 is the 27th National Eye Care Day. Since the establishment of National Eye Care Day in 1996, the country has been vigorously promoting the importance of eye health every year to enhance the public's awareness of eye care. However, in recent years, the incidence of myopia in Chinese people has been increasing year by year. As early as 2018, the number of myopic people in China had exceeded 600 million, and China has become the world's number one country with myopia. At the same time, the problem of myopia at a younger age is particularly worrying. According to data released by the National Health Commission, in 2020, the overall myopia rate among children and adolescents in my country was as high as 52.7%, including 14.3% for 6-year-olds, 35.6% for primary school students, 71.1% for junior high school students, and 80.5% for high school students.

There are many reasons for this phenomenon. On the one hand, the academic burden of teenagers in my country is heavy, they lack outdoor activities, and they overuse their eyes at close range for a long time, which makes the incidence of myopia increase with the increase of school age. On the other hand, the incidence of myopia is also related to race. For example, the incidence of myopia in Europeans (Caucasians) is about 30.6%, and the incidence in the American population (including whites and blacks) is 41.6%, while the incidence of myopia in Asians is much higher than that of other races.

Is myopia hereditary?

It is worth noting that myopia, like height, weight and body shape, is also significantly affected by genetics. In life, it is not difficult to find that when both parents are myopic (especially with high myopia greater than 600 degrees), even if they seriously limit the time their children spend watching TV and playing with mobile phones, their children are still likely to develop myopia early on.

Several foreign twin studies on myopia have shown that the inheritance rate of myopia is about 50%-90%.

How to find the "myopia gene"?

In order to find the "myopia gene", geneticists first used the method of family linkage analysis to identify 26 gene variation sites associated with the risk of myopia.

With the rapid development of genetic testing technology, the method of family linkage analysis has gradually become unfashionable, especially after the emergence of genome-wide association studies (GWAS). By comparing the distribution frequency of gene variants in myopic people and normal people, researchers have found more than 100 risk variant sites associated with myopia. These gene variants may change the endophenotypes such as axial length, corneal curvature and macular thickness by affecting processes such as neuronal synaptic transmission, cell adhesion and cell cycle, ultimately leading to the occurrence of myopia.

It is worth noting that although researchers have reported hundreds of myopia-related gene variants, how these gene variants cause myopia has not yet been fully studied. In addition, all these gene variants can only explain less than 20% of the heritability. Until now, there are still a considerable number of myopia-related gene variants that have not been discovered. These research results show that myopia is actually a very complex trait, and hundreds of "myopia genes" with small effects together lead to the formation of myopia.

How to prevent myopia scientifically?

We may not be able to change the innate factors, but we can still prevent and slow down the progression of myopia by changing our lifestyle. To prevent myopia, you can try the following:

1. Increase the time of outdoor activities

Studies have shown that increasing the time spent outdoors can significantly reduce the prevalence of myopia. Spending one more hour outdoors each week can reduce the chance of myopia by 2%.

2. Maintain the correct reading and writing posture, and achieve "one foot, one inch, one fist"

Reading and writing at close range for a long time will increase the incidence of myopia. We need to maintain a correct sitting posture when reading and writing, with the chest one fist away from the table, the eyes one foot away from the book, and the hand one inch away from the tip of the pen.

3. Balanced diet and balanced nutrition

Studies have shown that vitamin A, D and zinc deficiency and a high-sugar diet may induce the occurrence of myopia. Therefore, you can eat more green leafy vegetables, dairy products, soy products, fish, etc., eat less carbonated drinks and high-sugar sweets, and maintain a balanced intake of various nutrients.

4. Use of regulating paralytic drugs

Studies have shown that low-concentration atropine eye drops can slow the growth of myopia in children and adolescents by an average of 60% to 80%, so the use of low-concentration atropine is also an effective measure to prevent myopia. However, it should be noted that the use of low-concentration atropine requires the guidance of a professional ophthalmologist and should not be purchased and used blindly.

5. Use orthokeratology lenses

Orthokeratology lenses are currently a safe and effective method for controlling the progression of myopia. However, not everyone is suitable for using them. The use of orthokeratology lenses must be under the professional guidance of an ophthalmologist.

References

1.Wang YM, Lu SY, Zhang XJ, Chen LJ, Pang CP, Yam JC. Myopia Genetics and Heredity. Children. 2022; 9(3):382. https://doi.org/10.3390/children9030382

2. 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/iovs.18-25965

3. Wang YM, Lu SY, Zhang XJ, Chen LJ, Pang CP, Yam JC. Myopia Genetics and Heredity. Children (Basel). 2022;9(3):382. Published 2022 Mar 9. doi:10.3390/children9030382