Why does Grandpa have trouble seeing things?

When people get older, sometimes their eyes don't work as well as they used to. They may need to use eyeglasses, magnifiers, or other equipment to help them to see. They may also need brighter light to see well. And sometimes, they may wear dark glasses or a hat that has a brim because the light is too bright and glary, making it harder to see. They may also do things in new ways if they can't see well or can't see at all.