Eye patch is often used by people with lazy eyes. Lazy eyes is also known as amblyopia. It is a disorder of the visual system featured with a vision deficiency. And using eye patch is one of the method to help them. You can place a eye patch over the "good " eyes, thus to force the lazy eyes to work. It will help improve the sight in the lazy eyes. But there are a few study also shows: there maybe no extra benefit for people with lazy eye to wear an eye patch for more than six hours daily.
An eye patch is often worn for medical reason. It is often used by people who have a lazy eye to cover the good eye while leaving the other exposed. Besides, it is also worn to protect eyes with scratched corneas and strained eyes. An eye patch do have practical medical uses but also can work as a part of pirate costume, haha !
The eye patch is used for those kids who have lazy eyes (amblyopia). It's really a powerful tool to correct the lazy eyes without side effect. The lazy eye means one eye has normal vision, but the other one has port vision and can't develop to normal sight during childhood. The amblyopia is a common eye vision that some infant would have during their childhood. The eye patch can adjust the depth perception of eyes and improve the ability of poor eye to focus.