A subepithelial elastic lamina in the palpebral conjunctiva of monkeys.

Eyelids from ten cynomolgus monkeys were sectioned in a variety of orientations and the conjunctival layer examined by light and electron microscopy. An elastic lamina composed of a mesh of mature elastic fibres was present in the palpebral conjunctival stroma adjacent to the epithelium covering the area of the tarsal plate and extending to the lid margin. Mesh fibres orientated at or close to right angles to the lid margin were thicker and denser than the transverse and oblique fibres linking them. The elastic lamina was most substantial in the marginal conjunctiva bridging the interval between the tarsal plate and the mucocutaneous junction where it terminated abruptly. In this position the area occupied by the elastic mesh exceeded that of the mesh spaces. Dense collagen bundles enclosed the lamina, infiltrating the mesh spaces and attaching the lamina firmly to the tarsal plate. In the marginal zone thick elastic fibres branched forward from the lamina in a brush-like fashion penetrating the relatively soft marginal eyelid tissue obliquely between tarsal gland ducts, while other finer, more numerous fibrils passed backwards attaching the lamina to the basement membrane of the epithelium. The organisation of the elastic lamina suggests that the tension generated would act to pull the lid margins towards the surface of the eye. Production of a regular thin tear film during lid retraction following a blink is facilitated by this action.