The ocular surface: from physiology to the ocular allergic diseases.

Allergic conjunctivitis (AC) is an inflammation of the conjunctiva secondary to an immune response to exogenous antigens, usually called allergens. In fact, AC is a syndrome that involves the entire ocular surface, including conjunctiva, lids, cornea, and tear film. The signs and symptoms of AC have a meaningful effect on comfort and patient health, and could be influenced by environment, genetics and immune regulation mechanisms, all of which work together in a complex immunological homeostasis. Dysregulation in such immune responses could turn into a variety of ocular allergic diseases (OAD). This review describes some of the current understanding of cellular and molecular pathways involved in different OAD.