Well, in my opinion, it is possible to have headache when you suffer iritis. First, you should know what the iris is. The iris is made up of muscular fibers, which can control the amount of light entering the pupil. In that way, you can see clearly. And when it is inflamed, the ititis occur. And then it can just affect your eyes, also affect the related organs, such as head. Finally, you may suffer headache. For your situation, you can just try some ways to treat your iritis, so that your headache will recover too. For example, you should wear dark glasses if light worsens your eye pain. Also, you can take some mild analgesics, such as ibuprofen to help control some of the discomfort. Anyway, you can just have a try.