The inflammatory process of the uvea is called uveitis and may cause sight threatening damage to the eye. The aetiological factor in about 30% of the cases of uveitis is unknown. If established clinical entities without known cause, such as Fuchs' uveitis, are included, no aetiological agent or association with systemic disease can be identified in about 50% of cases.'Uveitis may be induced by infection, autoimmune disease, trauma, or malignancy. It is recommended that the different forms of uveitis should be classified according to their anatomical localisation-anterior uveitis, intermediate uveitis, posterior uveitis, and panuveitis." 3

The uvea plays an important role in the ocular immuno-logical defence mechanisms. Immunologically speaking the eye has a deviant and privileged position because of the blood-retina barrier, absence of lymphatic drainage, and a special feature called the anterior chamber associated immune deviation (ACAID). These special defence mechanisms contribute to the preservation of vision. 4 If these defence mechanisms fail, intraocular inflammation