The conjunctiva is a thin transparent epithelial membrane that lines the inner surface of the eyelids (tarsal conjunctiva) which folds thereby forming a sort of bag (conjunctival fornix or cul de sac) Finally, to coat the front and external dell 'eye (bulbar conjunctiva). The two portion conjunctival slide one on the other, lubricated by the tear fluid facilitating the movements of the eye. The inner corner of the eye, the conjunctiva folds back on itself forms a fold, the semilunar fold, and a rosy projection, fleshy, the caruncola lacrimale, containing accessory lacrimal glands and sebaceous glands. The conjunctiva is costituta by epithelial cells (columnar epithelium and squamous) arranged in 2-5 layers and stroma (richly vascularized connective tissue). Its main function is to protect the eyeball, thanks to the epithelial lining and allow this to constantly move freely in all directions and without disturbance of the friction of its surfaces thanks to the lubrication of tears. They are distributed throughout the conjunctiva different types of glands with specific functions for the production of the tear film glandular mainly formed by goblet cells which contain granules of mucin (goblet cells) that ensure the production of the internal mucous layer of the tear film, by sebaceous glands and serous glands (Dry eye ). The conjunctiva, you can find its conjunctival fornix numerous bacterial species (who live here generally without causing any disturbance), for its particular anatomy and almost continuous daylight exposure to dust, pollen, battery etc. in addition to the physical and biological protection of tears, is specifically equipped with defense mechanisms of the immune-mediated conjunctival tissue (lymphoid follicles) which is drained by the preauricular lymph nodes and submandibular. A breach of this particular balance in the conjunctival sac infection or external, or a form toxic-allergic may give rise to a slight reddening of the conjunctiva (hyperemia) or a more severe with abundant secretion, sorrow, foreign body sensation, and tearing sometimes associated with edematous swelling (chemosis), known, more or less by all, come conjunctivitis.