Create a sphere. Pull and condition (soften) enough clay to form a shape roughly the size of a golf ball for a life-sized eye model. Form it into a sphere on your work station by rolling it in circles between a flattened palm and the table beneath.
Shape the sphere into a slightly oblong shape. The human eye is not quite perfectly round but slightly avocado-shaped, with the pointed section at the front where the iris and retina are. Make this shape by positioning your flat hand toward the front half of the sphere shape and rolling the clay back and forth a few times on the work station.
Add clay for the iris. Pull a small piece of clay, roll it into a circle, then flatten it into a disc. Lay this onto the front of the eye and see if it looks like it's about the right size. Roll the clay back into a ball and adjust the amount you're using if it's not. Blend the disc piece into the surface of the sphere so that they're smoothly joined together.
Form the pupil. Create a circular indentation in the center of the iris using a toothpick.
Attach a short, cord-shaped piece of clay to the back of the eye to form the optic nerve. Make this by rolling a piece of extra clay into a “snake” on your work surface, then trimming a short piece and blending it into the back of the eye model.
Let the clay dry to hardness according to the instructions on the package.
Paint the model. Make the optic nerve a light red, the pupil black, and the iris in an appropriate eye color, such as blue or brown. Use red to paint on additional flat sections, such as veins. Use the drawing in "Resources" as a guide.