Not injected there. Andreno is heavy in iron. Collects in the blood stream. The eyes have smaller veins. The iron can't pass through as easily and sometimes gets collected there. Causing the eyes to start to darken. Surgery is the only way to remove the iron deposits. If left alone the whole eye will turn black. It's why demons have black eyes in folklore. They didn't have the medical knowledge how to remove the deposits. Child eaters where easier to identify before plastic surgery.