Please note: this is an older tutorial from 2000 and I will be updating it sometime soon I hope
This is one example of how I CG eyes using my WACOM art tablet and Photoshop. The same basic method can be used for any style of eye. This specific eye style is from my comic "Sexy Toast" (from the character "Jane").

1. I create a new image with a white background. I create a new later and draw the basic eye. Usually I do this with a 2 or 3 pixel airbrush and the "Soft" setting on my WACOM Intous.

2. Next I set my WACOM Intous to "Med" and add some lighter shading to the eye. If you are doing this with a different tablet or the mouse just set the opacity down on the airbrush.

3. I use the smudge tool to smooth out the eye.

4. I use a larger very solid airbrush to add in white highlights.

5. Since this is Jane's eye I add her special lower eyelashes.

6. I add a NEW layer behind my eye and use a soft airbrush and the smudge tool to create some background shading.

7. I create a new later ABOVE the others and set it for "color". Then I use the hairbrush to color the center of the eye green. You could also add eye shadow or other skin coloring at this point.

8. Because this is Jane she has skulls in her eyes. To add them I create another new later above all my others and draw small skulls. Then I set the Transparency down between 50% and 80% until it looks good... sometime I smudge or deform the skull a little. DONE!