And how does it affect mankind. It may come to a surprise and this article clipping by no means implies you should avoid seeing an eye-specialist.
There will be numerous opinions, from quack to whatever. Though, I believe in what is written in the attached, I do not want you to believe.
I post it so you can understand how this eye condition has been treated in Europe in the last centuries.
(I still prefer the alternative method to the modern method.)
Please read about cause and help.