Eye for detail

An old lady was nervous because her eyesight was failing and she was afraid that her friend whom she was expecting to marry might reject her. So, she comes up with a plan to prove to him that she can see perfectly. She puts a straight pin on a tree that is about 200 feet from her front porch. When her beau arrives, they sat in the porch swing and are talking when she suddenly stops the conversation and asks, "Is that a pin sticking in that tree?" Her friend squints his eyes and says, "I don’t see a thing." "Well, I’m going to go and see," she says as she jumps up, runs towards the tree, and collides with a cow.