The specific causes of iritis are as follows: a. Infectious factors. Bacteria, fungi, viruses, parasites, rickettsiae, etc. can be infected by direct invasion, or by inducing antigen, antibody and complement complex reactions, and can also cause immune reactions and inflammation by cross-reactions between pathogens and human or ocular tissues. Second, autoimmune factors. Normal eye tissue contains a variety of inflammatory antigens such as retinal S antigen, interphotoreceptor vitamin A class binding protein. When the body’s immune function is disrupted, immune reactions to these antigens can occur. Third, trauma and physical and chemical injury. Trauma and physical and chemical injury are mainly caused by activation of arachidonic acid metabolites. Fourth, immunogenetic mechanisms. For example, ankylosing spondylitis is closely related to HLAB27, and AC Harada syndrome is closely related to HLAD24 antigen.