Both the upper and lower lids have a thickness to them, as shown in the drawing to the right. The upper lid’s thickness is indicated by its cast shadow and by the appearance of an edge in one corner. The lower lid is a shelf that will often pick up light. If fact, in the outside corner of the eye, the shelf of the lower lid is often lighter than the white of the eye. Make sure that you haven’t made the shelf a single line, and that your lines aren’t showing when you are done shading.
Keep it neat
Before shading the eyes, erase the interior guide lines you have made. Leave the crosshairs in the iris, as you can use them in shading. ...