Conjunctiva & Limbus

Conjunctiva

Thin, semi-transparent, mucous membrane lining the inner surface of the eyelids

Functions:

• Lubrication (reduces friction between eyelids

• Antimicrobial

• Source of stem cells for corneal epithelium

Parts of the Conjunctiva

1. Corneoscleral limbus

2. Bulbar Conjunctiva

3. Forniceal Conjunctiva

4. Palpebral Conjunctiva

5. Puncta

6. Mucocutaneous Junction

Conjunctival sac

potential space between palpebral conj and bulbar conj

Subtarsal sulcus

• 2mm from posterior edge of the eyelid margin

• spans the inner surface of the eyelid

• traps foreign particles that enter the conjunctival sac

Plica Semilunaris

• Crescent shaped fold of bulbar conj

• unfolds when eye abducting

• vestigial remnant of nicitatng membrane “third eyelid” in other species

Caruncle

• Nodular tissue situated between plica semilunaris and the medial canthus

• Likened to non-keratinized skin

  • contains pilosebaceous unit with cilia, accessory lacrimal gland tissue, and numerous sebaceous glands

Glands of Krause

Deep subconjunctival tissue from the superior fornix to superior border of the superior tarsal plate

Glands of Wolfring

Larger than glands of Krause. tend to be located in the region of the tarsal plate and are more prominent nasally

Palpebral conj (histology

• stratified columnar epithelium

• stratified squamous epithelium

Fronix (histolgy)

• stratified columnar epithelium

Bulbar conj (histology)

• Stratified cuboidal epithelium

Mucocutaneous junction (histology)

• transitions to keratinized skin of eyelid

• Serves as source of stem cells for palpebral conjunctiva

Zonula Adherens

holds neighboring cells together

Zonula Occludens (tight junctions)

seals intercellular clefts forming intercellular permeability barrier

Conjunctival Epithelium

• Microvilli extend from apical surface

  • increase surface area for absorption and secretion

  • assist with stabilizing mucin layer of tear film

Goblet cells

• unicellular glands secret mucus layer of the tear film via apocrine secretion

• non-uniform distribution- most abundant in forniceal conjunctiva and nasal bulbar conjunctiva; sparse near limbus and lid margin

Autonomic Innervation

• parasympathetic = stimulatory

• Sympathetic = inhibitory

Crypts of Henle & Stieda

• goblet cell-lined surface grooves the palpebral conj proposed to be part of the conj associated lymphoid tissue system

• Function: trap bacteria and antigenic material, allow it to be neutralized by various defense mechanisms of the conj

Langerhans Cells

• immune cells

• 250-300 mm² (1/2 found in skin)

• 15 -20 mm² peripheral 1/3rd cornea

• non in central cornea

Dendritic Melanocytes

• common in heavily pigmented races

• produce pigmented ring at limbus

• protect stem cells at limbus from UV damage

• patches on bulbar conj

Corneal Stroma

• Fibrovascular matrix

• looser matrix in bulbar conj vs palpebral conj

• attaches to underlying tenons capsule

Contains: Nerves, Blood vessels, lymphatics

Conjunctival stroma (histology)

• firmly adherent to tarsal plate (cant be moved)

• stroma in palpebral conj has abundance of lymphoctyes and plasma cells that secret IgA

• sometimes organize to form follicles

• vascular structures in conj surrounded by mast cells that release granules containing histamine

Conjunctiva Stroma (Lymphatics)

• not appreciated in vivo

• lymphangiectasis may occur with chronic irritation of the conjunctiva

Surgical limbus

• transitional area of 1-2 mm in width where conrea merges with sclera

• appears as a blue-grey ring

• anterior margin of limbus corresponds to peripheral termination of descmet’s membrane (Schwables line)

• posterior margin where coloration gives way to white sclera responds to posterior limit of Schlemm’s canal at the scleral spur

Palisades of vogt

• conj epithelium transitions into corneal epithelium

• 8-10 layers thick

• stem cells for bulbar conj epithelium and conreal epithelium reside

• radial folds increase surface area for basal cell proliferation

Palisades of vogt (histology)

• radially oriented fibrovascular channels between ridges of thickend conjunctival epithelium

• fibrovascular channels contain, arterial, venous, and lymphatic vessels

• more prominent at superior and inferior limbus

Blood supply

• Palpebral conj - marginal and peripheral palpebral arcades (artery)

  • palpebral arteries originate from medial and lateral palpebral arteries and anastomose in eyelid

  • small collateral branches connect arcades to the tarsal plate

  • collateral arteries give it pinkish-red color

Vasculature of Bulbar conj

• Posterior conj arise from peripheral palpebral arcades

• anterior conj vessels arise from anterior ciliary arteries (7 total) which branch from muscular arteries to each rectus muscle

  • supply bulbar conj up to limbus

  • from superficial pericorneal vascular plexus (fenestrated)

Anterior Conj Arteries

• lateral rectus only has 1 anterior ciliary artery

• the rest have 2

Sub conjunctival hemorrhage

• rupture of a posterior or anterior conj artery

• typicall benign only require palliative treatment

• associated with valsalva, blood thinners, constipation, straining

Ciliary injection

• inflammation in deeper structures such as iris or ciliary body (uveitis)

• perforating anterior ciliary arteries that supply major arterial circle of iris become congested and show injection of perilimbal vascular plexus

• peripheral bulbar conj not injected as perilimbal region

Venous Drainage

• more numerous than the arteries

• Palpebral Veins or anterior ciliary veins —> muscular veins —> superior or inferior ophthalmic vein

lymphatic drainage

• lymph from lateral conj drains into preauricular lymph nodes

• lymph from medial conj drains into submandibular lymph nodes

Innervation palpebral conj

Upper palpebral conj

• CN V1 - Ophthalmic Division

  • Lacrimal Nerve

  • Supraorbital nerve (From frontal nerve)

  • Supratrochlear nerve (from frontal nerve)

Lower Palpebral conj

• CN V2 - Maxillary Division

  • Infraorbital nerve

Innervation of Bulbar Conj

Sensory

• CN V1 - Ophthalmic

  • Nasociliary Nerve

    • Long Posterior Ciliary nerves

Autonomic

• Postganglionic Sympathetics from carotdi plexus (constriction)

• Postganglionic Parasympathetic fibers from pterygopalatine ganglion

Sensory to caruncle

• CN V1 - Ophthalmic Division

  • Nasociliary nerve

    • Infratrochlear nerve

Hyperemia

looseness of substantia propria in the forniceal conj permits fluid accumulation (edema) accumulation of mast cells, lymphocytes, etc. in substantia propria

Follicles

lymphoid germinal centers vessels around the base

Viral = lymphadenopathy

Papillae

swelling of conj

fibrovascular core central vessel

nonspecific, mechanical + Allergic

Giant Papillary Conjunctivitis

Contact lens induced

Verneal (seasonal) keratoconjunctivitis

Pinguecula

Pterygium

• when removed they often come back

• can cause induced astigmatism