Fig. 7

The impacts of refinements in lens organization. (a) Image formed by a spherical glass bead with a single refractive index, showing the blurring resulting from spherical aberration. (b) The same image through the lens from a fish eye, which has a graded refractive index, resulting from a higher crystallin protein concentration in the centre than at the edges. Although the first “lens” may have functioned relatively poorly, it is only a matter of incremental adaptive changes to improve its functioning to the level seen in modern camera-type lens eyes. For images of eye lenses focusing light from a laser, see Piatigorsky (2007, 2008). From Sweeney et al. (2007), reproduced by permission of The Royal Society and A.M. Sweeney