The major component forming the eyelid crease is the supratarsal fusion of the orbital septum with the aponeurosis.
The lacrimal drainage system includes the upper and lower puncta, the lacrimal canaliculi, the lacrimal sac, and the nasolacrimal duct.
The eyelashes are arranged in 2 or 3 irregular rows along the anterior dermal edge of the eyelid margin.
The lacrimal gland undergoes structural and functional alterations with age, which may contribute to acquired dry eye syndrome.
The orbicularis oculi muscle is innervated by CN VII, the facial nerve.
It is a plane located posterior to the preseptal orbicularis oculi muscle.
The accessory lacrimal exocrine glands of Krause and Wolfring, which contribute to the aqueous component of the tear film.
The superior and inferior ophthalmic veins.
The marginal arterial arcade is located 2 mm from the free border of the eyelid, just above the ciliary follicles.
The outer lipid layer, secreted by the meibomian glands, helps reduce evaporation and stabilizes the tear film.
The glands of Zeis (modified sebaceous glands) and the glands of Moll (apocrine sweat glands).
They transport tears from the orbital lobe to the conjunctival fornix, emptying approximately 5 mm above the superior margin of the upper tarsus.
The medial drainage is received by the submandibular lymph node, while the lateral drainage is received by the preauricular lymph node.
The palpebral conjunctiva begins at the mucocutaneous junction of the eyelid and adheres firmly to the tarsus.
The Tenon capsule is composed of elastic connective tissue, compactly arranged collagen fibers, and a few fibroblasts.
The blood supply of the eyelids is derived from the facial system, which arises from the external carotid artery, and the orbital system, which originates from the internal carotid artery along branches of the ophthalmic artery.
The eyeball is an oblate spheroid with a corneal radius of curvature of 8 mm and a scleral radius of 12 mm. The anteroposterior diameter is approximately 23–25 mm.
The three concentric layers are the outer protective layer, the middle vascular layer, and the inner neural layer.
The uvea serves nutritive and supportive functions, supplying oxygen to the outer retina and producing aqueous humor.
The superior eyelid crease is present near the upper border of the tarsus, where the levator aponeurosis establishes its first insertional attachments.
The lacrimal puncta are small openings on the eyelid margin, located at the extreme nasal border of the eyelids at their junction with the medial canthus.
The five layers are epithelium, Bowman layer, stroma, Descemet membrane, and endothelium.
Because an operation on the inferior rectus muscle may be associated with changes in the palpebral fissure.
The tarsal plates consist of dense connective tissue, not cartilage.
A persistent membrane over the valve of Hasner can lead to excessive tearing and discharge in infants with nasolacrimal duct obstruction.
40 mm long.
It adheres firmly to the tarsus and plays a role in tear drainage.
The gray line, or intermarginial sulcus, corresponds histologically to the most superficial portion along the entire length of the free margin of the eyelid.
The blood-ocular barrier prevents extravasation of intravascular contents into the eye and consists of intercellular junctions of adjacent cells at various locations in the eye.
They are located in the conjunctiva and secrete mucus.
The main lacrimal gland is located in a shallow depression within the orbital part of the frontal bone.
Orbital, preseptal, and pretarsal.
The suspensory ligament of Lockwood, which is a fusion of the sheath of the inferior rectus muscle, the inferior tarsal muscle, and the check ligaments.
Sebaceous cell carcinoma is more common in the upper eyelid due to the presence of more oil glands in the upper eyelid than in the lower eyelid.
The lacrimal puncta and canaliculi are lined with nonkeratinized stratified squamous epithelium.
14–20 mm in length.
Oil (meibum) from meibomian orifices forms a reservoir on the skin of the eyelid margin and is spread onto the tear film with each blink.
The eyelid skin is one of the thinnest in the body and contains fine hairs, sebaceous glands, and sweat glands.
The anterior chamber, located between the iris and the cornea, is filled with aqueous fluid.
The limbus is the border that separates the cornea and the sclera, appearing blue-gray and translucent.
The three layers of the tear film are the outer lipid layer, the middle hydrophilic mucoaqueous layer, and the glycocalyx.
Glandular epithelial cells and myoepithelial cells.
The lower eyelid punctum sits closer to the corneal limbus due to the growth of the maxillary sinus, which draws it laterally.
The orbital septum inserts on the aponeurosis of the upper and lower eyelids.
They secrete an oily substance that helps to lubricate the eye.
Hemidesmosomes anchor the basal corneal epithelial cells to Bowman layer. Disruption at this level can lead to scarring and recurrent erosion syndrome.
Direct access to the cavernous sinus through the orbital venous system, potentially leading to inflammation and cavernous sinus thrombosis.
The inner glycocalyx mediates the interaction between the mucoaqueous layer and the surface epithelium, among other functions.
Lysozymes, lactoferrin, and immunoglobulin A.
The orbital septum arises from the periosteum of the bones of the orbital margin (arcus marginalis).
The parts of the conjunctiva include limbus (Li), bulbar conjunctiva (BC), forniceal conjunctiva (FC), palpebral conjunctiva (PC), and marginal conjunctiva (MC).
From the lesser wing of the sphenoid bone.
The fundamentals and principles of ophthalmology.
The bulbar conjunctiva is supplied by anterior ciliary arteries.
The venous drainage system of the eyelids can be divided into a superficial (or preseptal) system and a deep (or postseptal) system.
The action of the frontalis muscle of the brow.
The levator aponeurosis passes through the orbicularis oculi muscle and provides a minor contribution to the superior eyelid crease.
The Tenon capsule is thickest near the equator of the globe, which helps in suspending the globe in the orbit and stabilizing the position of the extraocular muscles during eye movements.
Cholinergic innervation helps stimulate secretions from the lacrimal gland.
The three geographic zones of the conjunctiva are palpebral (tarsal), forniceal, and bulbar.
It constitutes a major refractive element of the eye due to the difference in refractive index between air and the tear film.
The Tenon capsule forms the cavity within which the globe moves and helps establish a pulley system in the orbit.
The orbital part inserts into the medial canthal tendon and other portions of the orbital margin and the corrugator supercilii muscle.
The Müller muscle is responsible for a 2 mm lift of the upper eyelid.
It functions solely in forced lid closure.
Levator palpebrae superioris muscle.
They secrete mucin, contributing to the mucoaqueous and glycocalyx components of the tear film.
Conjunctivochalasis is the redundant folds of conjunctiva between the globe and the eyelid margin, often caused by loss of the Tenon capsule due to aging.
The gray line, or intermarginal sulcus, is visible between the bases of the cilia and the orifices of the meibomian glands.
The meibomian glands are associated with the orifices visible along the lower eyelid margin.
It indicates violation of the orbital septum.
The total volume of the average adult eye is approximately 6.5–7.0 mL.
Age-related connective tissue degeneration can lead to acquired strabismus, such as sagging eye syndrome, and loss of the Tenon capsule can result in conjuctivochalasis.
The caruncle is a small, fleshy, ovoid structure attached to the inferomedial side of the plica semilunaris.
The orbicularis oculi muscle acts as the main protractor of the eyelid and functions as a sphincter during voluntary closure of the eye.
Goblet cells secrete mucin, which is a component of the mucoaqueous layer of the tear film and the glycocalyx layer.
These muscles surround the canalicular system and lacrimal sac, driving tears into the system and down the duct with blinking.
They can profoundly affect the integrity of the ocular surface and the patient’s vision.
Meibomian glands are modified holocrine sebaceous glands oriented vertically in parallel rows through the tarsus.
The punctum of the canaliculus is located medially at the summit of each lacrimal papilla.
Aging is associated with an alteration in the lipid profile of meibum and with meibomian gland loss.
They produce oil (holocrine secretion).
The cornea provides the main refractive power of the eye and protects the internal ocular tissues.
The medial group drains into the submandibular lymph nodes, while the lateral group drains into the superficial preauricular lymph nodes.
Administering phenylephrine and α agonists, as they may stimulate the Müller muscle and falsely elevate the lid.
The Müller muscle attaches to the upper border of the upper tarsus and to the conjunctiva of the upper fornix.
The upper eyelid usually has longer and more numerous eyelashes than the lower one.
The lacrimal artery, a branch of the ophthalmic artery.
It provides support for the upper eyelid and surrounding tissues.
They are separated by the lateral horn of the levator aponeurosis.
27–30 mm long and 8–11 mm wide.
The retina has a dual circulation; the inner retina is perfused by the retinal vessels, while the outer retina is perfused by the choroid.
The posterior chamber is the anatomical portion located posterior to the iris and anterior to the lens.
The Müller muscle originates from the undersurface of the levator palpebrae superioris muscle in the upper eyelid.
It provides lubrication, facilitates the exchange of solutes, contributes to antimicrobial defense, and serves as a medium to remove debris.
The inferior punctum is approximately 6.5 mm from the medial canthus.
The plica semilunaris is a narrow, highly vascular, crescent-shaped fold of the conjunctiva located lateral to and partly under the caruncle.
Both are similar in width (29 mm) and thickness (1 mm), but the height of the upper tarsus (10–12 mm) is almost 3 times greater than that of the lower tarsus (4 mm).
It functions both voluntarily and involuntarily in spontaneous and reflex blinking.
The limbus houses corneal stem cells and is the site of passage of the collector channels that link the Schlemm canal to aqueous veins.
Episcleritis refers to inflammation in the superficial layer of the sclera, while scleritis involves the deep layer.
It is a thin sheet of connective tissue that encircles the orbit as an extension of the periosteum.
The innermost layer is the retina, which contains photoreceptors and neural elements for processing visual information.
The main segments include skin and subcutaneous connective tissue, muscles of protraction (orbicularis oculi), orbital septum, orbital fat, muscles of retraction (levator palpebrae superioris, Müller muscle), tarsus, and conjunctiva.
It acts as a retractor, arising from the capsulopalpebral head of the inferior rectus muscle and attaching to the lower border of the lower tarsus.
The caruncle is composed of modified cutaneous tissue, containing sebaceous glands and fine, colorless hairs.
These glands account for approximately 10% of the total lacrimal secretory mass.
The orbicularis oculi muscle can be divided into orbital and palpebral (preseptal and pretarsal) parts.
The palpebral conjunctiva is lined with nonkeratinized stratified squamous epithelium.
There is a single row of 30–40 meibomian orifices in the upper eyelid and approximately 20 orifices in the lower eyelid.
The eye contains three compartments: the anterior chamber, the posterior chamber, and the vitreous cavity.
The average depth of the anterior chamber is 3.11 mm.
The outermost layer consists of the clear cornea anteriorly and the opaque white sclera posteriorly.
The epithelium differentiates into a superficial columnar layer and a deep, flattened cell layer.
They produce aqueous secretion.
It is a small bundle of striated muscle fibers located at the eyelid margin, visible as the gray line.
15 mm.
The average volume of the anterior chamber is 220 μL.
It delimits the anterior or posterior spread of edema, inflammation, or blood, such as in preseptal cellulitis and orbital cellulitis.
The average volume of the posterior chamber is 60 μL.
The largest compartment is the vitreous cavity, which contains the vitreous gel and makes up more than two-thirds of the volume of the eye.
The uvea consists of the iris, ciliary body, and choroid.
