Our eye are probably the many important an essential structures we have actually in our body. They uncovered on the surface by a slim layer of skin and soft tissue called the eyelids. The eyelids serve multiple purposes including protecting the eyeball indigenous injury, managing the quantity of light the enters the eye and also constantly lubricating the eyeball through tears secreted by the lacrimal gland throughout blinking. All these attributes together aid maintain the structural integrity that the eyeball and protect castle from external influences.

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From an anatomical suggest of view, the eyelid consists primarily that skin, basic soft tissue also called a subcutaneous tissue and also a slim layer that muscle dubbed the orbicularis oculi. Under this muscle room other issues that divide the area into various planes. These are called septum and include the fibrous orbit septum and tarsi. In adds to to this, in order because that the eyelids to open up are lid retractors that assist assist blinking. Finally, there additionally exists a tiny amount of fat tissue as well. The eyeball is spanned by a slim layer of tissue referred to as the conjunctiva.

Anatomy that the eyelid

The description above only provides a superficial rundown of the anatomy that the eyelid. If one to be to look at the eyelid in a more detailed manner, a sagittal section taken across the eyelid will market a clear see of the assorted structures that form it. That course, it should be borne in mind the the structures that are visualised count on the airplane at i beg your pardon the sections are taken.

As stated above, the tissues deserve to be divided into planes by structures called the septum. The orbit septum differentiates the orbital tissue from the lid. Behind the septum space a number of different various other structures, a understanding of i beg your pardon is crucial if surgery is to be performed. In particular, it is crucial to determine the anterior and posterior lamellae. In essence, the anterior lamella is composed of the skin and also the orbicularis oculi muscle if the posterior lamella is composed of the conjunctiva and the tarsus.

Let’s take a look in ~ the frameworks of the eyelid in a bit an ext detail.


The eyelids

The upper eyelid starts in ~ the eye and also extends up words joined the skin of the forehead. It is distinguished from the forehead skin by the visibility of eyebrows. Similarly, the reduced eyelid starts at the eye and also extends to sign up with the skin that the cheek. ~ above close inspection, it is noticeable that the lord eyelid is a lot of looser 보다 the upper eyelid, specifically because the organization within the cheek that blends v the reduced eyelid is a lot of denser.

At the peak of the top eyelid is a wrinkles in the skin referred to as a skin folds or the remarkable palpebral sulcus. That lies about 8 to 11 mm over the margin that the upper eyelid and consists that fibres of the levator aponeurosis. Similarly, there additionally exists one more skin fold in the lower eyelid called the inferior palpebral sulcus. However, this skin wrinkles is often much more prominent in children and can become less influential as one gets older. Anatomically, the worse skin folds is seen about 3 to 5 mm listed below the outer facet of the lid margin.

The inner facet of the eyelid is called the inner canthal region. In ~ this an ar runs a wrinkles of skin referred to as the nasojugal fold. Native an anatomical allude of view, this fold lies in between the orbicularis oculi and also the levator labii superioris. To placed it in easier terms, the nasojugal fold is that area that the inner facet of the eye where tears role down and also can accumulate. The is additionally called the tear trough. Similar to the nasojugal fold is another fold the skin that is evident in the outer facet of the eyeball. This is dubbed the malar fold and runs native the outer element towards the nasojugal fold.

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When the eyes are open, the space between the upper and also lower eyelids is generally described together ‘fusiform’. This space is likewise called the palpebral fissure. Generally the palpebral fissure measures in between 28 to 30 mm large and approximately 9 come 10 mm in height. If one were to examine the palpebral fissure in a bit an ext detail, it would be obvious that the highest allude of the fissure lies at that suggest on the upper eyelid that coincides to a point at the inner aspect of the pupil. Younger individuals have the upper eyelid slightly higher than older people in whom it lies at about 1.5 mm below the margin that the eyeball called the limbus. Similarly, the lower eyelid lies at the border the the lower limbus.

There room two points at which the upper and lower eyelids meet. The one top top the inner facet is referred to as the medial canthus while the at the outer element is called the lateral canthus. Both that these have actually a unique angle at which the upper and also lower eyelids meet. As soon as examined along a horizontal plane, the medial canthal angle is located approximately 2 mm lower than the lateral canthal angle in Caucasians; that is 3 mm lower in Asians. The nose lies around 15 mm ~ above the within of the medial canthus.

In a nutshell, the palpebral fissure consists of the medial and also lateral canthus, the lacrimal papillae (part that the tear glands, additionally called lacrimal glands) and a small opening of the lacrimal glands v the reduced eyelid at the medial canthus referred to as the punctum lacrimale.

Skin and subcutaneous tissue

The eyelid is mainly made of skin. It is the thinnest skin in the body and also is less than 1 mm thick. In ~ the skin space a number of glands referred to as sebaceous glands that secrete an oily substance dubbed sebum. This glands are in larger numbers at the nasal element of the eyelid. If one to be to trace back the skin the the upper and lower eyelid, it would certainly be plainly evident that once it joins the forehead or the cheek, the texture of the skin changes and also becomes a lot thicker. Furthermore, the structure of skin is additionally different in ~ the various folds described above. Below the skin is a class of slim connective tissue dubbed a subcutaneous tissue (sub = under, cutaneous = skin).

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Underneath the skin, in addition to the subcutaneous organization is a slim layer the fat. However, the amount of fat is negligible when compared to various other parts that the body. Typically, subcutaneous tissue is lacking at points whereby the skin is attached straight to basic ligaments such as the medial and also lateral palpable ligaments. The skin and subcutaneous tissue have the right to be topic to details clinical problems such as dermatochalasis and blepharochalasis.

Orbicularis oculi muscle

The orbicularis oculi muscle plays vital part in the duty of the eyelids and additionally in face expressions. When it contracts and also relaxes, the skin over the muscle tends to move as well. The orbicularis oculi muscle is attached to the skin v fibres tissues that form what is called the superficial musculoaponeurotic system.

Broadly divided, the orbicularis oculi muscle consists of two main parts. The orbital part plays a function when the eyelids need to be strictly shut. It is further split into pretarsal and preseptal segments. The other part is dubbed the palpebral section that dram a duty in winking and also blinking. The muscle is supplied by the face nerve then divides into different branches to supply these different muscles. Anatomically, the facial nerve travel under the muscle groups and supplies it from under it surface.

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The orbital component of the orbicularis oculi muscle has a close connection with various other muscles responsible for facial expression. It originates native the inner margin that the orbit, additional attaching to the upper and also inner aspect of the orbit bone, the maxillary process that occurs from the frontal bone, the lower and also inner aspect of the orbit bone and also the frontal element of the maxillary bone. The course taken by the muscle is generally described together ‘horseshoe shaped’. The muscle fibres mingle with the surrounding facial muscles such together the corrugator supercilii and also the frontalis muscle. Together they travel around, they also interdigitate through the anterior temporalis fascia.

The preseptal part of the orbicularis oculi muscle consists of a superficial and also deep muscle head. The fibres of this section that lie within the upper and lower eyelid join and also the outer facet to type a structure dubbed the lateral palpebral raphe. The pretarsal part also has comparable origins and also its fibres operation under the lateral palpebral raphe, inserting into a bony structure at the outer facet of the orbit bone dubbed the lateral orbit tubercle through the lateral canthal tendon.

Submuscular areolar tissue

This is a loosened connective tissue that lies in ~ the orbicularis oculi muscle. That can form an anatomical plane that divide the eyelid into a front (anterior) and back (posterior) portion. The fibres the the levator aponeurosis climate passed through this plane in the top eyelid. A small part of this fibres contribute towards the advancement of the upper eyelid crease. Similarly, in the reduced eyelid, the fibres the the orbitomalar ligament passed through this plane.

If this anatomical airplane were to it is in tracked towards the eyebrow area, the retro-orbicularis oculi fat will be traversed. If the airplane were to it is in tracked towards the cheek, the sub-orbicularis oculi fat would be traversed.

Tarsi and Orbital septum

Tarsal plates

In order for the eyelids to keep their shape and also integrity, within them is dense fibrous tissue dubbed tarsal plates. Each of these tarsi is about 1mm thick and 29 mm in length. There space 2 main species of tarsi – the exceptional tarsus and also inferior tarsus. The superior tarsus is crescentic in shape and measures about 10mm vertically in its central aspect. The narrows outs together it traverses in the direction of the nose and outer element of the eyelid. Its reduced area is what forms the ago of the eyelid the lies beside the conjunctiva of the eyeball. Similarly, the inferior tarsus lies in the reduced eyelid, steps 3.5 – 5mm in elevation at the centre, and also lies in contact with the conjunctiva. Every of the tarsi are attached to the margin of the orbits v the medial and lateral palpebral ligament.

Within the tarsal plates space 25 tiny glands dubbed mebomian glands. These glands space as tall together the tarsus, and also they open up at a suggest just in former of the lid margin whereby the conjunctiva meets the skin (mucocutaneous junction). If one were to watch closely, lock lie behind a grey heat on the margin of the eyelid.

Medial palpebral ligament

Also dubbed the medial canthal tendon (MCT), the medial palpebral ligament is a band of fibrous organization that hold the inner element of the tarsal key in place. That is closely related to the orbicularis oculi muscle and also the tear ducts. The MCT is written of an anterior body which is created by a small component of the superficial facet of the orbicularis muscle the lies behind the tarsus. That traverses follow me a horizontal aircraft but is also attached to the frontal bone v a exceptional extension. The deeper component of the orbicularis muscle inserts into the back aspect the the lacrimal crest and also the lacrimal sac fascia. The fascia that the lacrimal sac is therefore closely concerned the various facets of the MCT.

Lateral palpebral ligament

Also referred to as the lateral canthal tendon (LCT), the lateral palpebral ligament is also a band of fibrous tissue that originates indigenous the tarsus, traverses outwards under the orbit septum and eventually inserts right into the lateral orbital tubercle (this lies roughly 1.5mm behind the lateral orbit rim). The LCT is about 10.5mm long and also 6.5 mm wide, and also at its midpoint attaches about 10mm below the frontozygomatic suture. The orbit septum and also the LCT room separated by a bag of fat referred to as the Eisler pocket. In adds to, the LCT is attached to the outer part of the orbital rim v a superficial airplane of fascia. This has been likewise called the superficial lateral canthal tendon and also helps to store the lateral canthus stable.

When traced above and below, the LCT attaches come the lateral horn the the levator aponeurosis above while the lower facet forms one arc whereby it attaches. During outer movement of the eye (abduction), the lateral canthal angle moves approximately 2mm together well, and this occurs due to the fibres that affix from the ago of the lateral check ligament that the lateral rectus muscle.

A structure called the lateral tarsal strap has actually been defined by Flowers. This is believed to be various to the LCT, and also connects the tarsal plate of the reduced lid to the lower, outer aspect of the orbit rim. Anatomically, that is a wide and quite sturdy structure. It lies simply 3mm below and also 1 mm behind the LCT, and 4-5 mm behind the anterior orbit rim. If excised, it permits for elevation of the lateral canthus.

Orbital septum

A septum regularly refers to a tape of organization that the end a structure. The orbit septum is a connective tissue band that attaches come the border of the orbital bone in ~ the periosteum (outer element of a bone). Within its central structure, the septum join the lid retractors at the lid margins. If one were to look in ~ the septum a lot more closely, it has a variety of layers (lamina) that are in close relationship with the anterior connective tissue framework. From a functional point of view, the septum has actually mobility similar to the eyelids.

We have already discussed just how the septum attaches to the lid margin. If one to be to trace the septum in an external direction (laterally), the is obvious that it is attached come the margin that the orbit, around 1.5mm in front of the attachments of the LCT. The orbital septum is separated indigenous the LCT by the previously disputed Eisler’s bag of fat. If traversing laterally, the septum runs along the rim of the orbit at the arcus marginalis. Once traversing over and in the direction of the nose, the septum runs across the supraorbital groove, in former of the trochlea and along the posterior element of the lacrimal crest. From an anatomical suggest of view, this place results in the septum lied in former of the medial inspect ligament and also behind the lacrimal sac and Horner muscle.

When tracing the attachments of the septum, it passes the lacrimal sac fascia, at some point reaching the anterior lacrimal crest in ~ a suggest corresponding to the lacrimal tubercle. It climate passes below this crest and also along the lower rim that the orbit, ultimately leaving the rim at a suggest beyond the zygomaticomaxillary suture. This results in production of a little space (recess) as result of its separation indigenous the zygomatic bone – this is dubbed the premarginal recess that Eisler, and also is filled through fat. Eventually, the septum reaches the lateral orbit margin at a suggest that lies just below the Whitnall ligament.

Another extension of the septum exists from the suggest where the orbit septum joins the levator aponeurosis. Explained by Reid et al, this extension travels over the tarsal plate and ultimately reaches the ciliary margin. The duty of this septum is to aid the levator aponeurosis, and also should it is in borne in mind when operating ~ above the eye.

Orbicularis retaining ligament

Also referred to as the orbit retaining septum or orbitomalar ligament, this ligament attaches the orbicularis oculi muscle come the reduced rim that the orbit. That is weak in its main aspect, and a lot stronger in the lower-outer aspect. Once traced laterally, the is contiguous through tissue that is created by fusion of the outer component of the orbicularis oculi and the deeper periosteum and temporalis fascia. This fusion is referred to as the orbit thickening. This orbital thickening consists the frontal procedure of the zygomatic bone.

As one gets older, the orbicularis retaining ligament has tendency to gain thinned out and stretched, v these changes much more prominent in the main aspect. Once excised along with the orbit thickening, it results in full release of the superficial fascia the lines the orbit rim.

Upper lid retractors

The upper lid retractors are a group of muscles whose main duty is the save the top eyelid elevated. The muscle that develops a part of this is referred to as the levator palpebrae superioris (LPS). This muscle originates indigenous the bottom aspect of the lesser soup of the sphenoid bone located within the skull. It consists of 2 heads – the levator muscle and also the remarkable rectus muscle. They space joined with each other by fibrous tissue. Native its origin, the LPS traverses horizontally front for about 40mm, finishing in an aponeurosis that is roughly 10mm posterior come the orbit septum. It climate takes a more vertical course towards the Whitnall ligament (superior transverse ligament).

The Whitnall ligament is comparable to the previously described orbital fascia and also lies in near proximity to the aponeurotic and also muscular junction that the LPS. It extends around the top margin of the orbit in a plane that lies in between the lacrimal gland fascia and also the trochlea. The LPS different in thickness, and is relatively thin in locations between the upper orbital rim and the Whitnall ligament.

When traced inwards and also outwards, the LPS aponeurosis develops ‘horns’ called medial and lateral horns. The lateral horn runs through the lacrimal gland, dividing it into 2 lobes – the palpebral lobe and the orbit lobe. Having actually done this, it goes on to affix to the lateral retinaculum situated at the lateral orbital tubercle. ~ above the other hand, the medial horn has actually a much more direct course and also is solved to the posterior lacrimal crest.

The aponeurosis eventually reaches the border the the superior tarsal plate having actually fused originally with the orbital septum. At the bottom finish of this fusion, a small part of the aponeurosis attaches to the lower facet of the anterior part of the tarsal plate. One component of this fusion extends forwards come insert right into the pretarsal orbicularis oculi muscle and skin, leading to the development of the skin crease in the upper eyelid.

Fat Pads

There are a variety of different fat pads the are current within and around the eyelid. One class of fat referred to as the pre-aponeurotic fat is found right behind the orbit septum and also in front of the levator aponeurosis. Also within the upper eyelid room two an ext areas that contain fat pads that space centrally and also medially (towards the nose) located. The medial fat pad is pale yellow in colour and also lies in former of the levator aponeurosis.

On the various other hand, the main pad that fat is broader and yellow in colour. Together it travel outwards, that wraps approximately the inner aspect of the lacrimal gland. The lacrimal gland deserve to be plainly seen and differentiated indigenous this fat by its pink colour and lobulated structure. The lacrimal gland is positioned simply posterior to the orbital margin however might prolapse contempt making it an ext prominent once the eye is examined.

While the above described the fat pads within the upper eyelid, the reduced eyelid fat pads room slightly different in structure. The worse oblique muscle off the main fat pad indigenous the dinner medial fat pad. There is a small amount that fat the lies in former of the worse oblique muscle as well. The inferior oblique muscle originates indigenous a little indentation in the reduced border the the orbital floor, relocating behind the orbital margin and also at the upper aspect of the sleep lacrimal canal. It overcome underneath the inferior rectus muscle and also through the Tenon capsule, ultimately inserting in ~ the allude close come the macula the the eye. This rather winding food of the inferior oblique muscle renders it fragile to injury during this section of the fat pads roughly the eyelid and also eye.

Blood supply

The eyelids are supplied by branches that the internal and external carotid arteries. The ophthalmic artery branches turn off the internal carotid artery and also supplies different parts that the eyelid. At the inner part of the top eyelid, the ophthalmic artery splits into two and also traverses outwards the supply both the upper and also the reduced eyelid. The branch that provides the lower eyelid is in truth a branch that arises indigenous the exceptional marginal vessel (that supplies the top eyelid). The superior and also inferior marginal vessels that arise indigenous the ophthalmic artery together type the marginal arcade.

The marginal arcade arteries are located at the former of the tarsus, 4 mm from the upper eyelid and also 2 mm from the lower eyelid margin each. The premium marginal arcade provides rise come a peripheral arcade the runs in former of the Muller muscle, providing it a superficial airplane and make it prone to injury during eyelid surgery. The peripheral arcade in the lower eyelid is frequently rudimentary.

Another branch that the interior carotid artery is the lacrimal artery that passes with the orbit septum along each eyelid and also ultimately join the marginal arcade.

While the over described the branches of the interior carotid artery, the outside carotid artery provides the eyelids together branches the the facial artery, infraorbital artery and also the superficial temporal artery. Every of this pride branches the anastomosis with other arteries ~ above the face. Because that example, the branch that the superficial temporal artery that provides the eyelids joins with the zygomatic branch and also transverse facial branch.

Lymphatic drainage

The lymphatic drainage the the eyelid is fairly extensive. The bulk of the top eyelid and also the outer half of the reduced eyelid drain into the pre-auricular lymph nodes, if a small component of the center of the upper eyelid and also the inner half of the reduced eyelid drains right into the submandibular lymph nodes.

Muscles

There are countless muscles about the eyeball that regulate of various movements. This muscles are referred to as extraocular muscles. They encompass the medial rectus, lateral rectus, inferior and also superior oblique and inferior and also superior rectus muscles. These are responsible because that the assorted directions of motion of the eyeball, including rotation that the eyeball. In ~ the eyelid, the levator palpebrae superioris is responsible because that elevation the the upper eyelid.

The extraocular muscles are gave by a selection of various cranial nerves. These incorporate the oculomotor nerve, the trochlear nerve and also abducens nerve.

Bones

The socket within which the eyeball is situated is called the orbit. That is a pyramidal shaped fossa that is developed by the blend of various orbital bones. These bones originate native the different aspects of the skull such together the frontal bone, sphenoid bone, zygomatic bone and the Palatine bones. In adds to, the maxillary bone and also the lacrimal bone also form a component of it. The arrangement of these bones is such that the walls are parallel to every other. The orbit steps 4 centimeter in height, 3.5 centimeter in width and also is approximately 5 cm in depth.

Within the orbit space a variety of blood vessels and nerves. This passed v the bone through miscellaneous openings called fissures. There room three key openings – the exceptional orbital fissure, the inferior orbit fissure and also the optic canal. Through these openings, various cranial nerves happen through and also supply the muscles and also blood vessels in the orbit. The exceptional orbital fissure permits for the passage of the frontal nerve, lacrimal nerve, nasociliary nerve and the recurrent branch the the lacrimal artery along with the remarkable orbital and also ophthalmic veins. The inferior orbit fissure enables for the passage of the infraorbital nerve, zygomatic nerve, infraorbital artery and also vein and parasympathetic nerve supplying the lacrimal gland. With the optic canal passes the optic nerve, main retinal vein and also ophthalmic artery.

Lacrimal gland

The lacrimal gland is responsible for tear production. The is separated by the levator aponeurosis right into an orbit lobe and a palpebral lobe. It has a characteristic appearance as has actually been previously described. That is gave by the lacrimal nerve which is a branch the the ophthalmic division of the trigeminal nerve.

The lacrimal gland secretes tears that are drained with a series of ducts. The lacrimal system is composed of lacrimal papillae, canaliculi, lacrimal sac and also naso-lacrimal duct. The canaliculus joins the lacrimal sac in ~ an edge which is protected by the valve that Rosenmuller.

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Connective tissue

We have already taken a quick look at the different species of connective organization that are seen in the eyelid and the structures roughly it. The fascia the is present about the eyeball divides the orbit into a variety of different connective tissue planes. Within each of these planes lie various structures. Having a expertise of the frameworks helps the operated doctor in locating them.