Figure 2. A vertebrate eye. Although there is considerable diversity among the eyes of various vertebrates, they all share some common features. In particular they have optical elements such as the cornea and lens which focus light in order to form an image on the retina. See Figure 14 for more on scleral ossicles such as are evident in this cross-section. (Drawing from Waldvogel, 1990, originally created by Virge Kask for Meyer 1977).