The eye has to be painted the right way in order for it to look round and real. Have you ever stood in front of a portrait and the eyes seem to "follow" you when you move from side to side? If you paint your eyes this way you will have those mysterious eyes and people will be amazed at how they will follow them!
1. The whites are never really "white" add a bit of flesh color to make them look accurate. The true value of the white area is closer to the value of the skin tone.
2. The eyeball is a sphere, that means it is round like a ball, not flat like a CD. You will accomplish this by carefully placing your shadows.
3. The highlight dot should always be placed very carefully. It should be just barely touching the Iris, not inside the Iris. If you see two highlights in the eye, limit the highlight to the most prominent one.
4. The upper lid will cast a shadow onto the white area and the Iris, it runs under the lid and around the sides of the white area of the eye. Add a bit of grey-blue to the white color for this shadow.
5. The reflected light is "directly" across from the highlight dot.
6. The outer edge of the Iris is a tiny bit darker than the rest of the Iris.
7. The upper lid is shadowed on the sides leaving a lighter color in the center, this makes it look like it is following the form of the eyeball.