Author(s): Vishrutha sushekar1, Viswanath B.N1, Shashidhar1, Ravi1, Mamatha1, Sandhya1
Allergic Conjunctivitis (AC) is the inflammation of conjunctiva in response to an allergen. It is one of the most common forms of conjunctivitis. Ocular allergies affect 6%-30% of the general population. Recent clinical observations suggests that ocular allergic response is not confined to conjunctiva but is a disease affecting the entire ocular surface including conjunctiva, lids(with their high content of mast cells), cornea, tear film(with its immunoglobulins) and lacrimal gland.
It is characterized by signs and symptoms ranging from itching, watering, redness, foreign body sensation, burning, photophobia, lid edema, conjunctival hyperemia, chemosis, watery or mucoid discharge, papillary reaction to severe sight threatening corneal complications.
The exposure of conjunctiva to an allergen initiates an immunological hypersensitivity reaction that heralds the onset of allergic eye disease. Early phase response occurs when allergen specific IgE binds to Fc receptors on surface of mast cells leading to its degranulation and release of pre formed mediators mainly histamine and newly synthesized mediators mainly PGD2. The released histamine binds to H1 receptor on cell surfaces of conjunctival tissue resulting in vasodilatation and increased vascular permeability which is responsible for itching, burning and tearing. Binding to H2 receptor results in increased mucus production at ocular surface. PGD2, considered being ten times more potent than histamine, increases conjunctival micro vascular permeability leading to redness, itching, chemosis and mucus production.