Are the eyes open or closed when the horse eats grass?

When the horse eats grass, his eyes are closed to avoid being stung by the grass.

Related celebrity anecdotes:

At that time, when Xu Beihong, a master of Chinese painting, was young, the painted horse was grazing on the grass with his head down and his eyes open. An old man looked at it and said, "This is a good picture, but it's a pity that this horse is blind." The master said, "How do you know this horse is blind?" The old man said, "The horse's eyes were closed when it rubbed its head in the grass, because it was not stung by the tip of the grass, but the horse opened its eyes." Isn't that blind? " ! "Xu Beihong was surprised after hearing this. So that's it. . .