The circular, colored curtain of the eye. Its opening forms the pupil. The iris helps regulate the amount of light that enters the eye.

The eye has a number of other key components including: the cornea, the pupil, the lens, the retina, the macula, the optic nerve, and the vitreous.

• The cornea is the clear front window of the eye that transmits and focuses light into the eye.
• The pupil is the dark aperture in the iris that determines how much light is let into the eye.
• The lens is the transparent structure inside the eye that focuses light rays onto the retina.
• The retina is the nerve layer that lines the back of the eye, senses light and creates impulses that travel through the optic nerve to the brain.
• The macula is a small area in the retina that contains special light-sensitive cells and allows us to see fine details clearly.
• The optic nerve is the nerve that connects the eye to the brain and carries the impulses formed by the retina to the visual cortex of the brain.
• The vitreous humor is a clear, jelly-like substance that fills the middle of the eye.

Greek: Iris (goddess)
Latin: (no equivalent goddess)

Either of two zones on the anterior surface of the iris, separated by a circular line concentric with the pupillary border.

A defect of the eye characterised by multiple holes in the iris.

The protrusion of the iris through an injury in the cornea of the eye.