Lens and ciliary body: anatomy, histology and action (preview) | Kenhub
Human Eye Structure: Eye Anatomy Explained
In humans and most mammals and birds, the iris is a thin, circular structure in the eye, responsible for controlling the diameter and size of the pupil and thus the amount of light reaching the retina. Eye color is defined by that of the iris. In optical terms, the pupil is the eye's aperture, while the iris is the diaphragm.