The eyes reveal most about the expression of the subject and is, therefore,
one of the most important part of a portrait. The shape of the eyes, the eyebrow,
and the muscle around the eyes are essential to capturing a person's resemblance.
The following are the eye elements of drawing eyes.
The first thing to note is the 'window' of light on the eye. Effective drawings of eyes almost always contain a light spot near the iris, where the light hits. Keep in mind that the eyeballs are not flat, but they are spherical and therefore require shading in the corners of the eyeball. Also, the top of the eyeball is usually darker than the bottom because of the shadow created by a higher light source and the eyelid.
The closed eye has a different approach than a regular eye. The eyelid covers an area that is curved, so the shadow from the side will curve inwards before blending in with the lighter areas. In certain situations, the light will hit the eyelashes creating a curved, light area.
As for the iris, its edges are darker than the interior. However the dark area is not simply an outline but involves a series of lines blended toward the interior. The pupil is the darkest area on the eye. When shading, start with that first.
Make sure that there is shading near the eyelid. The part where the eyes fold in is another dark part of the eye. This area goes deeper into the face so it will be lighter than the skin around the eyebrows. There should be thickness to the lower eye line, which is lighter than the area around it. Make sure that the shading for the 'bags' below the eyes are well blended, for they could alter the age appearance of your subject.
Last, but not least, the eyebrows and eyelashes are hairs, and should be done with a sharp pencil. Line the top of the eye before adding the eyelashes. Use single, quick strokes outward for each lash, and try to make it come to a point at the tip. The eyebrows should be shaded in lightly, with a layer of short strokes on top.