I really liked Chelsey's Eyeballs and wanted to do something similar with the stuff I had at home.
Needle felting balls is way easier than sewing them so that was the craft of choice.

1. Felted the white ball
2. Added the iris (just a solid circle of some colour)
3. Added the Pupil (smaller solid circle in the middle of iris, black)
4. Added the veins (thin strands of red, kind of wiggly and forking just wherever)
5. Added the optic nerve (braided three strands of wash & felt yarn, knotting and leaving the ends [~2cm], needle felted the braided part and needle felted the loose ends to the back of the eyeball, making more veins)

One might consider sewing through the optic nerve and the back of the eyeball with red (crochet) thread to make it more sturdy.
Also it would probably look better if the optic nerve was braided using four strands to get it to be round. I'll do that for the next ones. =)

I gave mine to my kitty and she totally loves them. =D Looks super gross when she rolls them through the house and tries to catch them. ^^

They look kind of wonky 'cause I had to use polyester wool instead of real wool for the white part. :( That stuff isn't exactly the best material to use for felting, but you gotta use what you have.