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Without a working appreciation of eyelid anatomy, you won't be able to fully benefit from the material to be presented. If you can glance into a mirror now and then while you're reading, the various descriptions will be a lot easier to follow.
External
The edge of either eyelid (the junction where the front and back sides join together) is called the eyelid margin. The eyelashes are located on the most forward edge of the lid margin.The palpebral fissure is the space between the upper and lower eyelid margins when the eyelids are open.
The points at which the upper and lower eyelids fuse together are called the commissures. The medial commissure is that point nearest the nose. The lateral commissure is on the other side closest to the temple.
The tiny openings to the tear drainage system are called the lacrimal puncta and are located on the eyelid margin just before the medial commissure.
The areas of "soft tissue" (skin, muscle, tendons, and fat) just beyond the commissures are called the canthi. The medial canthus starts at the medial commissure and extends about 1/2 inch towards the nose. The lateral canthus starts at the lateral commissure and extends about 1/2 inch towards the temple.
The upper eyelid crease in the indentation extending across the upper eyelid. The epicanthal fold is the small semicircular web of skin found over the inside corner of the lids most commonly in people of Asian descent.
Muscles of the Eyelid, Brow, and Face
The muscle that closes the eyelids is called the orbicularis muscle.
The main muscle that opens the eyelids is called the levator muscle. The levator muscle actually starts off deep in the socket, extends over the top of the eye, and then turns into a tendon (called the levator aponeurosis) as it connects to the eyelid.
The muscle of the forehead that pulls up the eyebrows is called the frontalis muscle.
The nasal muscles that pull the skin between the eyebrows down are called the procerus muscles.
The nasal muscles that push the skin between the eyebrows into vertical folds are called the corrugator muscles.
The six muscles that move each eyeball are called the extraocular muscles. The inferior oblique muscle may be encountered during the removal of lower eyelid fat.
Eyelid Support System
The easiest way to think of the lower lid support system is to imagine a hammock hanging between two trees. The equivalent of the main body of the hammock would be a thin cartilage-like structure that gives shape to the eyelid and is known as the tarsus or tarsal plate.
The tarsal plate is connected to the orbital rim of bone (the two trees) by a tendon on each side (the connecting ends of the hammock), known as the medial canthal tendon (on the side towards the nose) and the lateral canthal tendon (on the side towards the temple).
A similar basic support system exists in the upper lid.
The orbital septum is a fibrous membrane that can be thought of as holding back the fat that fills the socket and cushions the eyeball. In the lower eyelid, the orbital septum connects to the tarsus and extends all the way to rim of bone beneath the eye. In the upper lid, the orbital septum connects very near the top of the tarsal plate and extends all the way to the rim of bone above the eye.
Fat
If the orbital septum is stripped away, the eyelid fat will be exposed. The upper eyelid fat lies just in front of the levator aponeurosis.
The upper eyelid fat may be thought of as consisting of two pockets: a long thin middle fat pocket and a globular nasal fat pocket.
The lower eyelid fat may be thought of as consisting of three pockets, called the nasal, middle, and temporal fat pockets.
Eyelid fat is really an extension of the same orbital fat that fills the entire socket.
Deeper Eyelid
The eyelid fat sits just in front of the tendons of the main opening muscles and tendons (known also as the "retractors") of the eyelids.
The main opening muscle/tendon system in the upper eyelid is, as noted above, the levator muscle and aponeurosis. Small strands of tissue extending from the levator aponeurosis help to create the upper eyelid crease.
The main opening muscle/tendon system in the lower eyelid is called the capsulopalpebral fascia, which is a term we will try to use sparingly if at all.
The deepest layers of the upper eyelid consist of a minor retractor muscle (Müller's muscle). The back lining of the lid is known as the conjunctiva.
Socket
The eyeball is cushioned inside of a protective socket of bone, the rim of which is known as the orbital rim.
Bone has a thin but strong outer lining called periosteum, which is put to good use in some variations of advanced blepharoplasty.
The Midface
The tissues of the midface begin with the cheek and are thus not "formally" part of the eyelid. However, since the lower eyelid and cheek combine to form a single functional unit, the mention of several structures of relevance follows.
The suborbicularis oculi fat (SOOF) is a layer of fat located just beneath the lowest part of the orbicularis muscle of the lower eyelid. You'll find out later why it's important.
The malar fat pad is a larger layer of cheek fat starting just below the orbital rim of bone.
The numerous muscles of the midface, as well as their fibrous support system and surrounding fat pockets, have rather complicated names. For this reason, they are typically called soft tissues of the midface.
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