What do you mean, forty is free and fifty is blind?

Forty doesn't cost fifty to be blind, that is, when you are forty, your eyes are bright and your eyesight is good, but after fifty, your eyesight will get worse and worse.

Forty flowers and fifty blindness are common sayings according to the laws of human body. When human beings live to be about 50 years old, their internal functions will gradually weaken, among which the eyes are the most consumed organs in daily life, and their functions will weaken faster than other parts.