Eye types and shapes vary by doll type, so you do need to know the type of eyes to select a replacement pair along with the size you need.  If you don't know, we have a tutorial in our doll forum for finding out eye size by measuring both the the iris width and the length of the full eye.  Globe eyes are fully round with a stem at the back often used for dolls with an open socket so that you can change the direction of the iris to make the doll look in a certain direction.  Stationary eyes refers to a flat eye that often looks like the eye socket itself which are often oval in shape.  Blinking eyes mean that the doll eyes open and close when you tilt the doll backwards or forwards.  Eyes usually come in either acrylic or glass.