This is a semi realistic rendition of the human eye. It uses multiple shaders to give diffuse, glossy, translucent and other effects. Vertex paint has been used to guide the transition in IOR between the lens and other parts of the eye. Many aspects may be tweaked using the node groups in the materials.
The most significant element is the iris, which is realised by combination of simple materials, microdisplacement and a novel mesh which eschews the need for image textures. The appearance of the iris can be modified through two shape keys and the selection of colours in the iris material.