Smartphones have become widespread, and in recent years, even 3-year-olds own smartphones. It's common to see children using smartphones or tablets to watch YouTube. In this era, it's nearly impossible to avoid using smartphones or tablets, and we must adapt to the times.

I've been working in the IT industry for a long time, and spending long hours looking at PCs or smartphones can lead to memory issues, brain fatigue, and even addiction. The impact on small children is even more significant than what adults experience.

In recent years, research has shown two major negative effects on children:

1. Developmental disorders in the brain.

2. Smartphone strabismus (crossed eyes).

Regarding developmental disorders in the brain, I will provide a URL for reference.

What is particularly concerning nowadays is "smartphone strabismus" (internal strabismus), which is often observed in children under 12 years old. It can suddenly develop after using smartphones for around 3 hours a day.

In simple terms, when looking at a smartphone, the two muscles on either side of the eyeball (medial rectus and lateral rectus) are strained. Prolonged exposure in this state can cause the medial rectus muscle not to return to its original position.

Smartphone strabismus has both cases where it can be corrected and cases where it cannot, so caution is needed when allowing children to use smartphones.

It is well-known that Apple co-founder Steve Jobs and Microsoft co-founder Bill Gates did not allow their children to have smartphones until the age of 14. This highlights the potential toxicity of smartphones and tablets. Those working in the IT industry may resonate strongly with these concerns.

While completely eliminating smartphone and tablet usage may be impractical, it's essential for both children and adults, especially those in the IT industry, to consider distancing themselves from these devices as much as possible.