Not far from where my husband and I live is a farm with a lot of horses. During certain seasons, some of the horses have masks over their eyes. For a long time I felt sorry for the horses who weren’t allowed to see. But then I learned that my assumption about the masks was wrong. The masks are made of mesh, so horses can see through them. But flies, which cause eye disease, can’t get through them. The masks don’t keep the horses from seeing; they keep them from going blind!