Anatomical aspects of plastics of lower eyelids

In no other area of plastic surgery of the face is there such a delicate balance between form and function, as in the plastic of the eyelids. Given the subtle nature of the structural composition of the eyelids and their vital role in protecting the visual analyzer, iatrogenic interventions in the anatomy of the eyelids should be done carefully, accurately and with thoughtful consideration of existing soft tissue structures. To clarify some hidden points, a brief anatomical survey is required.

When the eye is at rest, the lower eyelid should fit well against the eyeball, the edge of the eyelid should go approximately tangentially to the lower limb, and the eye gap should slightly diverge upward from the medial to the lateral corner of the eye gap (the western shape). The lower palpebral groove (fold of the lower eyelid) is usually determined approximately 5-6 mm from the ciliary margin and approximately corresponds to the lower edge of the cartilaginous plate of the eyelid and the area of the passage of the pretarzal part of the circular eye muscle to the preseptal.

Plates

It is believed that the eyelids consist of two plates:

• an external plate consisting of the skin and the circular muscle of the eye,
• an internal plate that includes cartilage and conjunctiva.

The skin of the lower eyelid, having a thickness of less than 1 mm, retains its smooth, delicate structure until it spreads beyond the lateral edge of the orbit where it gradually becomes thicker and coarser. The skin of the eyelid, which usually does not have a subcutaneous layer, connects with the underlying circular muscle of the eye with thin connective tissue strands in the pretarsal and preseptal zones.

Musculature

The circular muscle of the eye can be divided into a darker and thicker ophthalmic part (arbitrary) and a lighter and thin palpebral part (voluntary and involuntary). The palpebral part can be further subdivided into preseptal and pretarsal components. The superficial, larger size of the head of the pretarsal part of the muscle unites, forming a tendon of the medial angle of the optic cleft, which penetrates into the anterior tear ridge, while the deep heads unite, penetrating into the tear-back crest. Lateral to the fibers are densified and tightly fixed to the orbital hillock of Whitnall, becoming a tendon of the lateral angle of the eye gap. Although the preseptal part of the muscle has attachments to the tendons of the lateral and medial corners of the eye gap, they do not have an ocular part - it is implanted subcutaneously in the lateral part of the orbit (taking part in the formation of the goose paw), covers some muscles that lift the upper lip and wing of the nose, and is attached to the bone of the lower edge of the orbit.

Directly below the muscular fascia running along the posterior surface of the preseptal part of the circular muscle lies the septum septum. Denoting the boundary between the anterior part of the eyelid (outer plate) and the inner contents of the orbit, it starts from the marginal arch, moving along the edge of the orbit (continuation of the periosteum of the orbit) and merging with the capsulopalpelabral fascia posteriorly, about 5 mm below the lower edge of the eyelid, it forms a single fascial layer, which is fixed at the base of the century.

Capsulopalpelpal head of the lower rectus muscle is a dense fibrous expansion, which, by virtue of its exclusive attachment to the cartilaginous plate of the eyelid, produces retraction of the lower eyelid while gazing downward. Ahead it surrounds the lower oblique muscle and, after reunion, further anteriorly participates in the formation of the supporting ligament of Lockwood (the lower transverse ligament, which here is called the capsulopalpelabral fascia). Although most of its fibers terminate at the lower edge of the orbit, some pass through the orbit of the orbit, participating in its subdivision into spaces, some penetrating through the preseptal part of the circular muscle, penetrating subcutaneously at the fold of the lower eyelid, and the rest go from the lower arch to the Tenon capsule.

Fiber of the orbit

Located behind the septum partition, inside the orbit cavity, the orbital fiber is classically segmented into separate zones (lateral, central and medial), although, in fact, there is a connection between them. The lateral fat pad is smaller and more superficial, and the large nasal pillow is divided by the lower oblique muscle into a more massive central space and an intermediate medial space. (During the operation, it is important not to damage the lower oblique muscle.) The medial cushion differs from the other constituents of the orbital fiber, consisting of a lighter color, a more fibrous and dense structure, and also the frequent presence of a large blood vessel in the middle. The orbital fiber can be considered as a fixed structure, since its volume does not correlate with the general physique and after removal is not restored.

Innervation

Sensitive innervation of the lower eyelid is mainly carried out by the infraorbital nerve (V2) and, to a lesser extent, subblock (VI) and zygomatic (V2) branches. The blood supply comes from the angular, infraorbital and transverse facial artery. At 2 mm below the ciliary margin, between the circular muscle and the cartilage of the eyelid, there is an edge arcade that should be avoided when performing a cut under the eyelashes.

Terminology

Specialists involved in surgery in this area should understand a number of descriptive terms widely used in the literature on eyelid analysis.

Blepharhalasis is often a misnomer. This is a rare disease of the upper eyelids of unknown origin, which is observed in women of young and middle age. Blepharhalasis is characterized by repeated attacks of painless unilateral or bilateral edema of the eyelids, leading to a loss of skin elasticity and atrophic changes.

Dermatochalasis is an acquired condition of increased pathological weakness of the eyelid skin, associated with genetic predisposition, the phenomenon of natural aging and environmental influences. It often combines with the loss of ophthalmic cellulose.

Steatoblepharon is characterized by the formation of a true or false hernia of orbital fiber due to the weakening of the orbital septum, which leads to the appearance of areas of focal or diffuse fullness of the eyelids. This condition and dermatochalasis are the two most common causes of patients' treatment for the help of surgeons.

Feston is a single or multiple folds of the circular muscle in the lower eyelid, overhanging one another, creating an outer bag resembling a hammock. Depending on the location of this bag can be preseptal, ophthalmic or zygomatic (buccal). It can contain fat.

Cheek bags are the areas of the sagging soft tissue on the lateral edge of the infraorbital ridge and the cheekbone prominence, directly above the furrow between the eyelid and the cheekbone. It is believed that they are the result of a symptomatic recurring edema of tissues with secondary fibrosis.

[1], [2], [3], [4], [5], [6]