Causes of Myopia?

Genetic Factor

Age Factor

Near Work vs
Outdoor Time

Hong Kong
Environmental Factor

Genetic Factor

If the parents are myopic, will their children have higher risk of developing myopia?

Both genetics and environment are main factors in the development of myopia. Children have a higher risk of developing myopia if both parents are myopic.

Is it impossible to prevent myopia if genes are a main cause of myopia?

Not really. Although genes are a factor that may cause myopia but myopia can be managed with proper eyecare by adopting good visual habits such as appropriate reading distance, proper lighting, balanced outdoor time along with suitable myopia control treatments.

Age Factor

The earlier a child develops myopia, the more likely the myopia will progress more aggressively. The ideal age norm of refractive error for children is:

    Up to Age 8 ≤ 0.50D of farsightedness
    Age 9 to 10 ≤ 0.25D of farsightedness

    Age 11 or
    Above

 0.00D or emmetrope

Therefore, if a child has less than 50 degrees of long-sightedness by the age of 7 to 8, the chance of developing myopia in the future is much higher.

Near Work vs
Outdoor Time

Prolonged near vision work (homework, reading, gaming) will increase myopia. Maintaining adequate time for outdoor activities under the sun can prevent/slow down myopia.

   Do Not
Read close up distance < 20 cm
Read continuously > 20 minutes
Do
 Daytime outdoor activities ≥ 1~2 hour/day

Hong Kong
Environmental Factor

Prevalence of myopia in Hong Kong is one of the highest in the world. Huge amount of homework, higher education level, ethnicity factor, compacted housing environment and the lack of outdoor space and so on, all contribute to a much higher myopia prevalence in Hong Kong compared to western countries.

The prevalence of myopia among the 12 years old children in Hong Kong is 61.5%.

Gifford, K. L., Richdale, K., Kang, P., Aller, T. A., Lam, C. S., Liu, Y. M., … & Sankaridurg, P. (2019). IMI–clinical management guidelines report. Investigative ophthalmology & visual science, 60(3), M184-M203.

Yam, J. C., Tang, S. M., Kam, K. W., Chen, L. J., Yu, M., Law, A. K., … & Pang, C. P. (2020). High prevalence of myopia in children and their parents in Hong Kong Chinese Population: the Hong Kong Children Eye Study. Acta ophthalmologica, 98(5), e639-e648.