I was asked how to do a fursuit eye that was easy, customizable, and well ventilated. Plastic canvas is great for some of that, but doesn't have the solid look that other materials do for the white of the eye and iris.

I turned to craft 'floam' or thin colored sheets of foam. It's easy to cut, comes in thin sheets and glues with pretty much anything.
The entire area in the front of the head is black plastic canvas.

To determine the location of hte pupils, I taped a sheet of paper to the front of the face where the eyes would be, then put the head on and looked into a bright light. Holding a black marker, I could poke at the paper where the center of each eye would need to be. Take the head off and there was my guide. Cut out circles of the right size and I had a template to use for the white floam eye whites and a simple ring for the iris.

I'm very pleased with the results.