Ankylosing spondylitis causes iritis when the systemic immune response to ankylosing spondylitis involves the iris. Ankylosing spondylitis occurs in young adults and is an autoimmune disease that mainly involves the middle-axis joints. In addition to mainly affecting the spine, middle-axis bones, and large joints of the limbs, the disease will also cause a systemic immune response as the disease progresses, which will then affect the eyes, skin, intestines, heart, lungs, and other multi-systems and organs, and when the disease affects the iris, the patient will suffer from iritis. Patients with ankylosing spondylitis complicated by iritis will have symptoms such as tearing, photophobia, eye pain, blurred vision, etc. However, the occurrence of iritis is not obviously related to the disease activity of ankylosing spondylitis, and both eyes usually have successive onset and recur alternately, so medications can be targeted to treat the symptoms. It is recommended that patients with ankylosing spondylitis complicated by iritis go to the rheumatology department of a regular hospital and follow the doctor’s instructions.