Inflammation of the iris is called iritis (the iris is the part of the eye that determines its color), and sometimes the ciliary body behind the iris can become inflamed as well. When the iris becomes inflamed, tiny white cells in the inflamed area and too much protein from the small blood vessels in the eye float in the atrial fluid between the iris and cornea. If there are too many cells floating in the atrial water, they attack the back of the cornea and also settle in the atrial water. The cause of iritis is unknown. One eye or both eyes may be affected. So, what are the causes of iritis? The following are the causes of iritis: 1. Herpes virus infection (20%): If you have herpes zoster on your face, especially on the forehead or cheeks, it may cause iritis. Other infectious diseases, such as toxoplasma infection, histoplasmosis, tuberculosis, syphilis, etc., may be associated with other types of iritis. 2. Genetic susceptibility (5%): Those who carry the HLA-B27 gene are more likely to develop certain autoimmune diseases, such as ankylosing spondylitis, Lyttle syndrome, inflammatory bowel disease, and psoriatic arthritis, due to alterations in this specific gene, which is closely related to human immune function. These diseases can be complicated by acute iritis. 3. Juvenile rheumatoid arthritis (15%): Pediatric patients with juvenile rheumatoid arthritis may develop chronic iritis. In children with milder disease and less involvement of only a few joints, iritis may serve as one of the first signs predicting the disease. Since these two diseases are closely related, physicians should often routinely screen for iritis or other types of uveitis in children with rheumatoid arthritis. 4, Ocular trauma (25%): Blunt, penetrating, or burn injuries to the eye (including chemical or thermal burns) can cause acute iritis. 5, posterior uveitis (20%): that is, inflammation that occurs at the back of the eye, which may spread to the front of the eye and cause iritis.