Get a picture of eyes like the one above. Or a single eye will do. Print it out. Then draw a line from corner-to-corner of each eye. Now, here's where you start seeing, not just looking. See how much "eye" there is above the line and how much below it.
Look at the shape of the so-called whites of the eye. When you draw an eye, your drawing of the shape of the whites must match those of the original. Also notice that the eyes on an individual aren't necessarily a mirror image of the other. There are some variations, and often more pronounced on an older person. Check out the shape of the inner whites of her eyes in the photo above.
Eyes are a problem because they are so important that the left brain has a stylized version to pop into place on your drawing that has nothing to do with the person you are trying to draw. I call it the football with a bullseye syndrome.
Hope this helps.
