Seen from the side, the iris widens from a narrow black oval, when we are looking straight ahead (A), to an ellipse, when we are looking somewhat to the side (B). The amount of space between the iris and the eye corner steadily decreases. When the glance is directly to the side (C), the iris fills our view of the eye. Its shape appears more circular, and white space has appeared on its far side. It's also widened the eye corner slightly (D). The rim of the upper lid bulges above the iris (A and B) when the lid travels over the tiny mound of the cornea.
The cornea is a transparent dome sitting on top of the iris. It has a subtle effect on the drawing of the eye. In the level gaze, the lower lid crosses so low on the dome (A), that its curve reflects only the ball underneath. The upper lid, however, crosses a part of the dome where it is higher off the ball (B). It is this slight bulge that we see when the gaze shifts from side to side. The cornea also creates the sharp dip in the lower lid when the gaze turns downward.
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