I have wood turned a human eye. The white of the eye is maple composed of 10 segmented rings. The iris is cherry, birch, and walnut in a fine segmented ring. The pupil is a piece of ebony.
image/text credit: frank howarth
I made the iris ring then trued it up on the CNC router to a circle to fit perfectly into the maple white of the eye. I made two irises and put one on each side of the eye. This way I could have two eyes with one eyeball.
I turned the eye on the lathe using a method of turning where one turns each of the 3 axes of the eye. This process of turning each axis is repeated in the same order until a perfect sphere is formed.
The finish I used was 2 layers of lacquer for a bottom coat. Then I added a top coat of 2 layers of wax. This brought out the contrast in the Iris but did not darken the maple. It gave the eye a nice shine like it is wet.