The Conjunctival Biopsy
Conjunctival tissue is rarely excised with enucleations so most material submitted is as scrapings or biopsies. Infection such as herpes simplex, molluscum or chlamydia may be diagnosed in conjunctiva scrapings. Atopy may also result in papillary conjunct
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Functional Anatomy The thin film-like nature of the mucous membrane is best appreciated during separation of the bulbar conjunctiva from the surface of the eye at surgery or during an autopsy. From a firm attachment at the limbus of the cornea, the mucous membrane is reflected around the fornices to cover the inner surface of the lid as far as the junction with squamous epithelium (white line) on the lid margin just posterior to the emergence of the lashes (see Fig. 10.1).
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The stability of the tear film depends on the presence of the acid and neutral glycosaminoglycans that form a hydrophilic layer on the microplicae on the surface of the superficial cuboidal epithelial cells. This layer is disturbed in conditions in which the tear film is depleted and the mucosubstances form clumps on the surface of superficial cells, which become stratified (Fig. 11.3b). It is noteworthy that the conjunctival epithelium has a remarkable capacity for regeneration and this tissue heals quickly after surgery.
Stroma Surface Epithelium The conjunctival epithelium consists of a basal layer of cuboidal cells, surmounted by a layer of wing cells (Fig. 11.1a), which differentiate into a surface cuboidal cell layer. In many conditions the surface layer becomes stratified (Fig. 11.1b) and this metaplasia is the source of pathology akin to that of epidermal stratified squamous epithelium (i.e., the progression to squamous carcinoma). The basal layer contains dendritic melanocytes and Langerhans cells and there are often scattered inflammatory cells within the basal layers. Goblet cells are found within the wing cell and surface cell layer. While the conjunctival epithelium reacts in inflammation in the same way as any other mucous membrane, it is noteworthy that in corneal inflammation, inflammatory cells pass through the limbal conjunctival epithelium to attach to the corneal surface (Fig. 11.2). The surface of the epithelial cells is thrown into microplicae, which are coated with mucosubstances, demonstrable by ruthenium red in the transmission electron microscope (Fig. 11.3a). The mucosubstances have not been identified precisely, but it appears that they are secreted by epithelial goblet cells, the acinar cells in the lacrimal gland and the accessory lacrimal glands, which each contain both acid and neutral glycosaminoglycans. In elderly patients, the goblet cells become trapped in the deeper layers of the epithelium and the secretions accumulate to form periodic acid-Schiff (PAS)/Alcian blue circular bodies. F. Roberts, C.K. Thum, Lee’s Ophthalmic Histopathology, DOI 10.1007/978-1-4471-2476-4_11, © Springer-Verlag London 2014
The conjunctival stroma contains blood vessels, nerves, lymphatics and a scattered lymphocytic infiltrate in the tarsal and bulbar parts: lymphoid aggregates form follicles in the fornix with advancing age and exposure to exogenous antigens. An awareness of the presence of stromal inflammatory cell infiltration in normal tissue is important in assessment of the significance of inflammatory reactions in the
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