I turned this simple ball pattern into eyeballs.
Round 1 -black
Round 2 -lighter color
Round 3 -darker color
The rest in white.
Add a stitch of white from middle of black through the color to create a shine line.
Add red thread as veins

Used the larger hook for the first round, it just makes the stitches a bit bigger and easier to crochet into in the next round. I think I crochet pretty tight so you might not need to do this if you crochet looser.