This chapter starts with a description of the optics of camera-type eyes, in which an image is projected upon a retina with cornea and lens as refracting elements. Ray tracing is explained with the human eye as an example of a terrestrial vertebrate's eye. Then the comparison is made to camera eyes of aquatic and amphibious animals, with an explanation of different kinds of aberrations, difficulties in accommodation to air and water as external media, and different solutions to these problems. A brief section deals with feedback regulation of eye development, and another one with eyes of particularly high light sensitivity. A section on compound eyes explains the difference between apposition and superposition eyes. It is pointed out that geometric optics (ray optics) is not adequate for analyzing the function of the small components of these eyes and an introduction is given to waveguide and mode theory. This is followed by sections on antireflective nipple arrays, eyes with reflective optics, scan-ning eyes, and the chapter concludes with a treatise of the evolution of eyes.