The conjunctiva can be divided into 3 geographic zones: palpebral (tarsal), forniceal, and bulbar (see Fig 1-35). The palpebral conjunctiva begins at the mucocutaneous junction of the eyelid and covers the lid’s inner surface. This part adheres firmly to the tarsus. The tissue becomes redundant and freely movable in the fornices (forniceal conjunctiva), where it becomes enmeshed with fibrous elements of the levator aponeurosis and the Müller muscle in the upper eyelid. In the lower eyelid, fibrous expansions of the inferior rectus muscle sheath fuse with the inferior tarsal muscle, the equivalent of the Müller muscle. The conjunctiva is reflected at the cul-de-sac and attaches to the globe. The delicate bulbar conjunctiva is freely movable but fuses with the Tenon capsule as it inserts into the limbus.
Anterior ciliary arteries supply blood to the bulbar conjunctiva. The palpebral conjunctiva is supplied by branches of the marginal arcades of the eyelids. The superior peripheral arcade, running along the upper border of the eyelid, sends branches proximally to supply the forniceal conjunctiva and then the bulbar conjunctiva, as do the posterior conjunctival arteries. The limbal blood supply derives from the ciliary arteries through the anterior conjunctival arteries. The vascular watershed between the anterior and posterior territories lies approximately 3–4 mm from the limbus.
The innervation of the conjunctiva is derived from the ophthalmic division of CN V.
The conjunctiva is a mucous membrane consisting of nonkeratinized stratified squamous epithelium with numerous goblet cells and a thin, richly vascularized substantia propria containing lymphatic vessels, plasma cells, macrophages, and mast cells. A lymphoid layer extends from the bulbar conjunctiva to the subtarsal folds of the eyelids. In places, specialized aggregations of conjunctiva-associated lymphoid tissue (CALT) correspond to mucosa-associated lymphoid tissue (MALT) elsewhere and comprise collections of T and B lymphocytes underlying a modified epithelium. These regions are concerned with antigen processing.
The thickness of the conjunctival epithelium varies from 2 to 5 cells. The basal cells are cuboidal and evolve into flattened polyhedral cells as they reach the surface. The goblet cells (unicellular mucous glands) are concentrated in the inferior and medial portions of the conjunctiva, especially in the region of the caruncle and plica semilunaris. They are sparsely distributed throughout the remainder of the conjunctiva and are absent in the limbal region. For further discussion of the limbus, see Chapter 8.
The caruncle is a small, fleshy, ovoid structure attached to the inferomedial side of the plica semilunaris (see Figs 1-24, 1-35). As a piece of modified skin, it contains sebaceous glands and fine, colorless hairs. The surface is covered by nonkeratinized stratified squamous epithelium.
Excerpted from BCSC 2020-2021 series: Section 2 - Fundamentals and Principles of Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.