Opening the eye extra wide with the levator palpebrae acts to intensify many of the expressions. But even in an otherwise relaxed face, the contraction or relaxation of the levator can have a drastic effect.
A. Excited. The eyelids are open as wide as possible. Most eyes will show a bit of white above the iris with the levator fully contracted. The lids arch more sharply, and the eye has a staring quality.
B. Alert. These eyes are open somewhat wider than normal. The iris begins to be covered by the upper lid (above).
C. Neutral. This is the ordinary, awake state for this person. The iris is still cut off quite high; more than half is showing.
the force of gravity, begins to drop down over the iris. If the levator relaxes completely, the upper lid will fall against the lower lid, closing the eye. The contracting levator will reopen the eye; if it continues to contract, the lid will rise past its normal open position to expose more eye than usual.
The levator is a sort of "intensity control" for the face. In the case of anger, fear, or surprise, the more vivid the expression, the more the eye will open. And the opposite is true: the more the eye closes, the more lackluster the face.
The crucial element in gauging the state of the eye is the shape of the iris, and white showing around it. Because the contrast between the dark iris and the bright eyeball is so strong, whatever that state is shows up from a long way off. We are the only animal with such a conspicuous eye display.
D. Sleepy. This iris is exactly half hidden. The relaxation of the levator allows the lid to fall. The pupil is partly blocked. This is a transitory state; we cannot stay conscious for long once our lid has fallen this low.
E. Losing consciousness. A momentary state. Either the person has just awakened or is just falling asleep. With this much of the pupil blocked, vision is seriously impaired. The iris is two-thirds covered.
F. Eye closed. When the levator is completely relaxed, the eyes close. The curved line of the lower lid becomes the line for both lids. The joined lashes are more prominent, and though lashes are often left out of drawings of the face (being so delicate), in this case their doubled thickness makes them a substantial enough form to include.
The Eye-squeezing Muscle: Orbicularis Oculi_
There are times when we wish to pull the eyelids closed. When we squint, or squeeze our eyes shut, we are using the orbicularis oculi. When it contracts, the eye, and often a much larger area of the face, including the cheeks and the mouth is affected. This is very unlike the modest action of the levator.
The orbicularis oculi is a large oval-shaped muscle, encircling the eye and spreading into the cheek beyond. It takes up the area that would be covered by a good-sized eyepatch. Clearly, when this muscle contracts, it's going to take a lot of face with it.
Imagine a large circle. Within it there are more circles, each one smaller than the last. The outer circle represents the boundaries of the orbicularis oculi; the lines within it trace the paths of its muscle fibers. The fibers travel in upward or downward arcs from one end of the eye to the other. All the fibers are fixed to the side of the bony nasal bridge; their free ends are attached to the skin of the cheeks and at the outer corner of the eye.
When the orbicularis contracts, the skin around the eye is pulled in toward the nasal bridge. The eye begins to close, and the familiar crow's feet appear at the outer eye corner. The more the fibers of the muscle shorten, the stronger the contraction, and the smaller the oval around the eye gets. The smaller it gets, the tighter the eye is closed and the more the skin wrinkles. Eventually, the eye is closed so tight it becomes hard to tell the eye line from the wrinkle lines. When the orbicularis is that strongly contracted, it also bulges up the cheeks, deepens the nasolabial folds, pulls on the corners of the mouth, and sometimes lowrers the brow.
The orbicularis oculi has distinct functional areas. The center of the muscle, where muscle fibers run through the eyelids themselves, is one independent region, the palbebral portion. Surrounding this is the remainder of the muscle, the orbital portion, which has two independent halves, upper and lower. The lower half, below the eyelids, is a key component of the smile; the upper half is used only when all portions of the muscle contract at once, as in the expression of pain.
The palpebral portion of the orbicularis oculi runs through the thin skin of the eyelids. It is attached to the bony inner wall of the orbit. This portion is so tiny that its full contraction leaves only the slightest of flexion wrinkles (those that form at right angles to muscle pull) in its wake. Its major effect, when tensed, is to tighten and compress the eyelids. When the eyelids are tightened, the only movement they can make is toward each other; that is, they begin to close.
Typically, the mild contraction of the palpebral muscles pulls the lids in just enough to give the eye a narrowed look. The lower lid closes more than the upper, taking on a more rounded, defined look. This narrowing lower lid movement is important in two very dif-ferent expressions: anger and happiness.
Many people do not have voluntary control over this portion. Those that do have smiles that look sincere, even if they are not.
Try squinting so that just one eye is partly closed. If you can do it, you'll observe that the cheek, particularly the upper part, rises; a smile-shaped crease appears below the eye; crow's feet appear at the outer eye corner; and the eye narrows. This narrowing is usually absent in an insincere smile. Amidst all these changes, the area above the eye is left relatively undisturbed; all the action is below.
If you squeeze hard enough, you can close the eye completely. This is what happens in the laugh. But don't squeeze so hard that your brow starts lowering. If you do, it means you've also triggered the upper half of the muscle.
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