Conjunctiva

• Thin mucous membrane
• Embryology: derived from surface ectoderm
• Continuous with the skin at the lids and with the corneal epithelium
• Goblet cells throughout especially in the fornices and plica semilunaris 
• Concentration declines with age
• Accessory lacrimal glands (of Krause and Wolfring) throughout lamina propria
• Identical to lacrimal gland in histology
• Gland of Krause in the superior fornix
• Gland of Wolfring at superior tarsal border
• These accessory glands provide basal tear production 
• Contains network of dendritic (Langerhans) cells
• Conjunctival sac has 25-30 microlitre capacity
• Tight junctions between cells prevent travel of electrolytes from tears 
• Conjunctival epithelium and goblet cells rely on vitamin A and retinoids 
• Abnormal in vitamin A deficiency leading to severe dry eye disease

Conjunctival layers

• Epithelium:
• 2-7 layers
• Non-keratinised stratified 
• Squamous over palpebral and limbal surfaces
• Columnar over bulbar surface
• Goblet cells, melanocytes, dendritic cells, lymphocytes
• Microvilli on the apical surface harbour glycoproteins that stabilise the tear film
• Epithelial basement membrane: type IV collagen, anchoring fibrils and hemidesmosomes
• Stroma:
• Loose connective tissue
• Superficial lymphoid layer: attached to epithelium via the BM

• Deep collagenous fibrous layer: attached to Tenon’s capsule over bulbar surface and posterior lamellae over palpebral surface

Arterial supply

• Palpebral arches supply most of the conjunctiva
• Anterior ciliary arteries (from the muscular branches) also supply the limbal conjunctiva

Venous drainage

• Match the arteries and drain into superior and inferior ophthalmic veins

Lymph

• Laterally to the superficial parotid nodes
• Medially to the submandibular nodes

Nerve supply

• Superior palpebral and forniceal conjunctiva: frontal and lacrimal branches of ophthalmic nerve (CNV1)

• Inferior palpebral and fornical: lacrimal branches (ophthalmic) supplies laterally and the infraorbital nerve (CNV2) supplies medially

• Bulbar: long ciliary nerves (branches of nasociliary from ophthalmic)

Palpebral (tarsal) conjunctiva

• Firmly attached to tarsal plates
• Stratified squamous epithelium
• Continuous with keratinised epithelium of the skin just posterior to the tarsal glands

Forniceal conjunctiva

• Attached to fascia of the extraocular muscles, therefore the conjunctiva moves as the globe moves

• Lacrimal ducts of the palpebral lobe of the lacrimal gland open into superior fornix
• Lateral fornix extends 14mm from the limbus to the equator
• Contains accessory lacrimal glands of Krause and Wolfring
• The superior fornix extends further from the limbus (ie. is deeper) than the inferior

Bulbar conjunctiva

• Loosely attached to sclera
• Columnar squamous epithelium but converts back to squamous at the limbus
• Conjunctival limbus is situated 1mm anterior to the corneoscleral limbus
• Fused with Tenon’s capsule 3mm from the limbus 

• Note: Tenon’s capsule fuses with the sclera a bit further forward, 1.5mm from limbus