Dr Agarwals’ Step by Step Oculoplastic Surgery Amar Agarwal, Athiya Agarwal, Sunita Agarwal
INDEX
×
Chapter Notes

Save Clear


Anatomy of the LidsChapter 1

Sunita Agarwal
Athiya Agarwal
Amar Agarwal
zoom view
2
 
INTRODUCTION
The eyelids are two modified folds of skin closing the front of the orbit and protecting the globe of the eye.
 
SURFACE ANATOMY
The upper lid is limited above by the eyebrow, which forms a definite anatomical boundary. The lower lid merges somewhat indefinitely to the cheek, the junction being indicated by two cutaneous wrinkles. These are the nasojugal folds (Fig. 1.1) running downwards and outwards from the inner canthus and a less defined Malar fold running downwards and inwards from the outer canthus. These two folds indicate the junction of the loose tissue of the lower lid with the denser structures of the cheek. Thus, they mark the line along which the fascia is anchored between the muscles of the lid (orbicularis oculi) and those of the upper lip (quadratus labii superioris).
zoom view
Fig. 1.1: Surface anatomy of the lids
3
These boundaries above and below, tend to limit effusions in the lid owing to this anchoring of the fascia.
The upper eyelid is divided by the superior palpebral furrow into an orbital portion above and a tarsal portion below. The inferior palpebral furrow, present on the skin of the lower lids is less distinct. It is formed by the fibrous slips that arise from the fascia surrounding the inferior rectus muscle and are inserted into the skin.
 
EYEBROWS
The eyebrows along with the eyelids form a part of the protective mechanisms of the eye. The two eyebrows are horizontally placed over the superciliary edge of the frontal bone, separated from each other by a smooth hairless prominent area known as glabella. In some individuals, the two eyebrows meet in the center above the root of the nose—a condition known as synophrys.
Each eyebrow from anterior to posterior (Fig. 1.2) consists of the following layers.
  1. Skin: The skin of the eyebrow is thick and contains numerous sebaceous glands, hair follicles and a few eccrine sweat glands.
  2. Subcutaneous tissue: The subcutaneous tissue in the eyebrow region has little fat, is mostly fibrous in nature and firmly binds the skin to the underlying muscles. Small movement of these muscles is therefore transmitted directly to the eyebrow skin and overlying hair, which move accordingly.
  3. Layer of striated muscle: The striated muscles, which move the eyebrow, are as follows
    • Frontalis muscle: This arises from the epicranial aponeurosis and is inserted by fine slips directly into the posterior surface of the eyebrow skin. The temporal branches of the facial nerve supply it.
      4
      zoom view
      Fig. 1.2: Anatomy of the eyebrows
      Its action is to elevate the eyebrow and thus indirectly cause elevation of the upper eyelid.
    • Orbicularis oculi: The orbital part of the orbicularis, which is inserted into the skin of the eyebrow, is called the superciliaris muscle. The temporal branch of the facial nerve supplies it. Its contraction draws the entire eyebrow downwards and slightly moves it medially.
    • Corrugator supercilii: It arises from the medial end of the superciliary ridge and lies beneath the frontalis and orbicularis muscles. It is inserted into the deep surface of the skin of the central part of the eyebrow.5 It receives its nerve supply from the temporal branches of the facial nerve. Its contraction draws the medial portion of the eyebrow downwards and medially, thereby producing vertical folds in the skin above the root of the nose, giving an expression of frowning.
    • Pyramidalis muscle: It arises as a part of the medial part of the frontalis and is inserted into the skin of the lower part of the forehead near the midline. Branches of the facial nerve supply it. Its action is to pull down the medial part of the eyebrow, creating horizontal furrows over the bridge of the nose, which accentuate the expression of frowning.
  4. Submuscular areolar tissue: Lying deep to the layer of striated muscles is a layer of areolar tissue, which separates the muscles from the galea aponeurotica.
  5. Aponeurosis: It covers the entire scalp area and at the eyebrow it forms the deepest layer. It is separated from the periosteum covering the frontal bone by a layer of loose tissue, allowing a free movement between the two.
 
EYELIDS
The length of the adult palpebral fissure is 25 to 30 mm. The two eyelids meet each other at the medial and lateral angles or outer and inner canthi. There is an intermarginal sulcus of von Graefe (Fig. 1.3) which is a fine gray pigmented line anterior to which the eyelashes take origin and posterior to which lie the orifices of the tarsal glands. Medially is the caruncle and plica semilunaris.
 
STRUCTURE OF THE EYELIDS
From without inwards each eyelid consists of the following layers (Fig. 1.4).6
zoom view
Fig. 1.3: Intermarginal sulcus
zoom view
Fig. 1.4: Structure of the eyelid
7
  • Skin
  • Layer of subcutaneous areolar tissue
  • Layer of striated muscles
  • Submuscular areolar tissue
  • Fibrous layer
  • Layer of nonstriated muscle fibers
  • Conjunctiva.
 
Skin
The skin is extremely delicate and highly elastic. At the junction of the skin and the conjunctiva is the gray line. On the lid margin the following structures are seen.
Hair follicles: They conform to the general type of hair follicle seen elsewhere. The eyelashes are arranged in 2 to 3 rows.
Glands of Zeiss: They are sebaceous glands associated with the cilia. Each opens into the follicle of the cilium by a short wide duct. Secretion of the Zeiss gland is called sebum and this prevents the eyelashes from becoming dry and brittle. It also contributes towards the oily layer of the tear film.
Glands of Moll: They are sweat glands, which are unusually large and lie between the cilia. The gland of Moll has a duct, which can open into the duct of the Zeiss gland or in-between two lashes.
Meibomian or tarsal gland: These are modified sweat glands and are arranged in a single row numbering 20-30 in each lid. They consist essentially of straight tubes running perpendicularly to the lid margin embedded in the tarsal plate and occupying almost its entire thickness. The tube is closed at its inner end and its outer end opens directly on the inner side of the gray line or intermarginal sulcus of von Graefe. Into the central canal open 10 to 15 acini from the 8sides. Secretions of the meibomian glands are oily in nature (sebum). The functions of this are
  • The oily marginal tear strip prevents the overflow of tears across the lid margins
  • Forms the oily layer of tear film over the cornea and bulbar conjunctiva. This prevents evaporation of tears and allows smooth movements of the eyelids over the globe
  • Ensures air-tight closure of the eyelids
 
Subcutaneous Areolar Tissue
Beneath the skin is a layer of loose areolar connective tissue, containing no fat. Edema or blood thus readily distends it. The overlying skin may be mobilized easily during plastic surgery.
 
Layer of Striated Muscle
Layer of striated muscle consists of two muscles— orbicularis oculi and the levator palpebrae superioris.
 
Orbicularis Oculi
Introduction: It is an oval sheet of concentric muscle fibers covering the lids and the regions of the forehead and face around the orbital margin.
Divisions: The orbicularis oculi can be divided into different parts (Fig. 1.5).
Pars orbitalis: This surrounds the orbital margin (Fig. 1.6). It arises from the anterior part of the medial palpebral ligament and the adjacent bones, namely upper orbital margin medial to the supraorbital notch, the maxillary process of the frontal bone, frontal process of maxilla and the lower orbital margin medial to the infraorbital foramen.
9
zoom view
Fig. 1.5: Divisions of the orbicularis oculi
zoom view
Fig. 1.6: Orbicularis oculi
10
From this origin, the muscle fibers sweep superiorly and inferiorly covering the orbital margins in the form of a large ellipse and meet at the lateral palpebral raphe. Superiorly, deep to the eyebrow the orbicularis fibers intermingle with those of the frontalis and thereby gain insertion into the skin of the eyebrow. The upper medial fibers of the orbital part, which pass to the skin of the upper eyebrow, are termed as the musculus superciliaris. Inferiorly, the medial and lateral peripheral fibers of the orbital part, which are attached to the skin of the cheek, are called musculus malaris. The orbital fibers help in forced closure of the eyelids and thus pull the eyebrows downwards.
Pars palpebralis: This forms two half-ellipses, one on each lid. Its fibers arise from the medial palpebral ligament and from the bone above and below it. They run as a thin sheet under the skin of the lid to terminate at the lateral commissure by interlacing with their fellows of the other lid to form the lateral palpebral raphe. It is divided into two parts—the one lying in front of the orbital septum and the other lying in relation to the tarsal plate.
Pars septalis: This arises in a broad origin from
  • Frontal process of the maxilla in the region of the anterior lacrimal crest
  • Superficial aspect of the medial palpebral ligament
  • Deep aspect of the medial palpebral ligament.
These last fibers being closely related to the lacrimal sac have been called the anterior lacrimal muscle.
Pars tarsalis: This is divided into three portions
  • Pars lacrimalis
  • Pars ciliaris
  • Pars subtarsalis.
11Pars lacrimalis: They pass as a thick band behind the lacrimal fossa in company with the deep part of the medial palpebral ligament. It arises from
  • Posterior lacrimal crest
  • Periosteal roof of the fossa covering the lacrimal sac.
It is also known as muscle of Horner, or posterior lacrimal muscle or tensor tarsi.
Some of the fibers are short and are inserted into the tarsal plate and into the connective tissue around the lacrimal canaliculi. The majority of the fibers run across to the lateral raphe.
Pars ciliaris: Along the margin of the lid an isolated fasciculus of fine fibers runs behind the ciliary follicles, which separates them from the rest of the muscle. It is known as pars marginalis (Fig. 1.4).
Pars subtarsalis: A few similar fibers run behind the opening of the ducts of the tarsal glands. It is also known as muscle of Riolan (Fig. 1.5).
Nerve supply: Seventh nerve.
 
Action
  • The orbital portion is voluntary and is called into play on forcible closure of the lids.
  • The palpebral portion acts alone in gentle closure of the lids as in sleep or in blinking which is involuntary.
 
Levator Palpebrae Superioris
Origin: At the apex of the orbit from the lesser wing of the sphenoid above the annulus, its origin blending with that of the superior rectus and medially with that of the superior oblique.12
Course: It runs forwards under the roof of the orbit and upon the superior rectus. The medial borders of the two muscles are adherent by fascial sheaths. It terminates in an expanded aponeurosis in the upper lid (Fig. 1.4).
Insertion: The levator palpebrae superioris (LPS) has a complex insertion.
 
Principal insertions
  • Cutaneous: The main bulk of the aponeurosis passes into the upper lid as radiating connective tissue fibers, which are inserted into the skin, and into the lower third of the anterior surface of the tarsal plate. These fibers pass between the orbicularis oculi muscle.
  • Osseous: The extremities of the aponeurosis remain tendinous and form two horns, which find attachment to bone at the midpoints of the lateral and medial orbital margins. The lateral horn which is the stronger and cuts deeply into the lacrimal gland and is inserted at the orbital tubercle of the zygomatic. The lateral horn divides the lacrimal gland into orbital and palpebral parts. The medial horn, which is the weaker and passes over the reflected tendon of the superior oblique, fuses with the medial palpebral ligament and thus finds a secondary attachment to the maxillary and lacrimal bones.
 
Secondary insertions
  • To the upper margin of the tarsal plate by some of its terminal fibers and by a lamella of smooth muscle, i.e. Muller's muscle
  • To the conjunctiva in the region of the fornix by means of its fascial sheath which becomes fused with that of the superior rectus. By this means, the conjunctival fornix is raised by either muscle simultaneously with movement of the lids on the globe.
13Nerve supply: Third nerve.
Action: Elevation of the upper lid.
 
Submuscular Areolar Tissue
Submuscular areolar tissue is a layer of loose connective tissue present between the orbicularis muscle and the fibrous layer (consisting of tarsal plate and orbital septum). The nerves and vessels of the lid lie in this layer and so to anesthetize the lid, injection is made in this layer.
There is a pretarsal space, which is bounded anteriorly by the levator aponeurosis and posteriorly by the tarsal plates. There is a preseptal space which is bound anteriorly by the orbicularis oculi and posteriorly by the orbital septum and above by the preseptal cushion of fat.
 
Fibrous Layer
Fibrous layer consists of the tarsal plates and the orbital septum.
 
Tarsal Plates
Introduction: They are two plates of dense connective tissue one in each lid, which are curved to conform to the shape of the globe of the eye.
Upper plate: The upper tarsal plate is large and D-shaped with a horizontal lower border coextensive with the ciliary portion of the lid margin and a curved upper border in the substance of the lid. It is 10 to 12 mm broad in the middle.
Lower plate: This is smaller and band-shaped. It is about 5 mm broad in the central region. The extremities of each plate meet in the commissure of the lids and continues to the orbital margin as the medial and lateral palpebral ligament (Fig. 1.7).14
zoom view
Fig. 1.7: Fibrous layer
 
Relations
  • Inner surface—closely adherent to the conjunctiva
  • Outer surface of the upper plate—covered by the LPS which finds attachment to its lower third
  • Outer surface of the lower plate—covered by the orbicularis oculi
  • Upper border of the upper plate—superior palpebral muscle of Muller is inserted there
  • Lower border of the lower plate—it receives the insertion of the orbital septum and the fascial expansion from the inferior rectus with the inferior palpebral muscle.
15Medial palpebral ligament: It is a broad band of connective tissue formed by the junction of the two tarsal plates on the medial side. It breaks into two parts that is, an anterior and a posterior part. The anterior part of the medial palpebral ligament lies in front of the lacrimal fossa and is inserted into the anterior lacrimal crest. The fibers of the orbicularis oculi take origin from it. The posterior part runs behind the lacrimal fossa and gets attached to the posterior lacrimal crest.
Lateral palpebral ligament: This is a single band formed by the junction of the lateral extremities of the tarsal plates. It is attached to the orbital tubercle of the zygoma just within the midpoint of the lateral margin of the orbit.
 
Orbital Septum
(Syn: Septum orbitale of Henle, Lid aponeurosis of Arnold, Large tarsal ligament of Winslow, or Palpebral fascia of Schwalbe)
Introduction: It is a thin membrane of connective and elastic tissue attached to a thickened line of periosteum around the orbital margin called the arcus marginalis of Charpy (Fig. 1.7).
 
Attachments
  • Centrally—it becomes continuous with the convex borders of the tarsal plates.
  • Peripherally—it is attached to the orbital margins.
  • Laterally—the septum is superficial and is attached to the orbital margin in front of the lateral palpebral ligament.
  • Medially—it lies deep near the posterior lacrimal crest from where it runs downwards on the lacrimal bone behind the Horner's muscle and thus lies deep to the 16lacrimal sac and medial palpebral ligament but in front of the medial check ligament. The line of attachment then crosses the lacrimal fascia (covering the lacrimal sac) at about its middle to reach the anterior lacrimal crest at about the level of the lacrimal tubercle, from where it follows the lower orbital margin.
  • Superiorly—the attached borders of the orbital septum follow the posterior lip of the upper orbital margins.
  • Inferiorly—the attachment of the orbital septum follows the lower orbital margins.
 
Relations
  • Anterior relations—anterior to the orbital septum is the submuscular areolar tissue, the layer of striated muscle, the subcutaneous areolar tissue and the skin.
  • Posterior relations—in the upper lid the septum is in close contact with the orbital fat, which separates it from the lacrimal gland, the levator muscle and the tendon of the superior oblique muscle. In the lower lid, the septum again is in relation to the fat, which separates it from the expansions of the inferior rectus and inferior oblique muscles.
 
Structures piercing the orbital septum
  • Lacrimal vessels and nerves
  • Supraorbital vessels and nerves
  • Supratrochlear artery and nerve
  • Infratrochlear nerve
  • Dorsal nasal artery
  • Superior and inferior medial palpebral branches
  • Tendon of levator
  • Expansion of the inferior rectus.17
 
Layer of Nonstriated Muscle Fibers
Introduction: They are two small sheets of plain fibers one in each lid—superior palpebral muscle and inferior palpebral muscle.
Superior palpebral muscle: This is known as the Muller's muscle. It is a thin band which arises from the under surface of the LPS in elastic tendons springing from among the striated fibers of this muscle. It runs downwards and forwards between the levator and the conjunctiva to be inserted into the upper margin of the tarsal plate.
Inferior palpebral muscle: This is much less definitely marked. It arises from the fascial sheath of the inferior rectus and from its expansion to the inferior oblique. Running upward towards the lower fornix it breaks into two lamellae. One of this finds attachment in the bulbar conjunctiva, while the other enters the lower lid where it is associated with the expansion of the sheath of the inferior rectus and is inserted into the tarsal plate.
 
Nerve Supply
Sympathetic nerves: Sympathetic irritation leads to the retraction of the lids and paralysis leads to Horner's syndrome.
 
CONJUNCTIVA
The palpebral conjunctiva forms the posterior most layer of the eyelid. It is firmly adherent to the posterior surface of the tarsal plate and Muller's muscle.18
 
GLANDS OF EYELIDS
  • The meibomian gland
  • Glands of Zeiss
  • Gland of Moll
  • Accessory lacrimal gland of Wolffring—These are microscopic accessory lacrimal glands present along the upper border of the superior tarsus and along the lower border of the inferior tarsus. These are about 2 to 5 in the upper lid and 2 to 3 in the lower lid.
 
NERVES OF THE EYELID
The nerves can be motor, sensory or sympathetic. Figure 1.8 explains the nerve supply of the eyelids.
 
ARTERIAL SUPPLY OF THE EYELIDS
Figures 1.9 and 1.10 explain the arterial supply of the eyelids. The eyelids are mainly supplied by the medial and lateral palpebral arteries, which are branches of the dorsal nasal and lacrimal arteries. Each medial palpebral artery anastomoses with the corresponding lateral palpebral artery to form the marginal arterial arcade. These lie in the submuscular plane in front of the tarsal plate some 2 to 3 mm away from the lid margin, in each eyelid. In the upper eyelid another arcade is formed from the superior branches of the medial palpebral artery. This lies near the upper border of the tarsal plate.
The arteries, which supply the lids, are the external carotid artery and the internal carotid artery. From the external carotid artery the branches which supply the lids are the facial artery, superficial temporal artery and the maxillary artery (infraorbital branch). The branches of the internal carotid artery, which supply the lids, are the dorsal nasal artery, frontal branch, supraorbital artery and the lacrimal artery.19
zoom view
Fig. 1.8: Nerve supply of the eyelids
 
VENOUS DRAINAGE
There are two sets of plexus of veins in the lids. They are the pretarsal venous plexus and the post-tarsal venous plexus.
 
LYMPHATIC DRAINAGE
There are two sets of plexus of lymphatics in the lids. They are the pretarsal lymphatic plexus and the post-tarsal lymphatic plexus.
20
zoom view
Fig. 1.9: Tabular column to show the arterial supply of the eyelids
The lymphatic vessels are arranged into a medial and a lateral group. The medial group drains into the submandibular lymph nodes and the lateral group into the parotid lymph nodes.
 
BELL's PHENOMENON
The Bell's phenomenon is a highly coordinated reflex between the facial and oculomotor nuclei, whereby on closure of the eyelids, the eyeball is rotated upward and outward.
21
zoom view
Fig. 1.10: Arterial supply of the eyelids
This is a protective mechanism that brings the cornea up under the covering eyelid and away from the impending danger. Although the exact pathway of Bell's phenomenon is not known, it is clear that the pathway is different from that for the voluntary upward gaze, since Bell's phenomenon may be present in supranuclear paralysis of upward gaze.22
Bell's phenomenon is not present in 10 percent of otherwise healthy persons and therefore its absence is not necessarily a sign of disease. Further, in some individuals an inverse Bell's phenomenon is present, whereby the globes rotate outward and downward on attempted closure. When inverse Bell's phenomenon is associated with lagophthalmos (inability to close the lids) severe corneal drying and ulceration (exposure keratitis) may occur.