The iris is the colored part of the eye that surrounds the pupil and controls the amount of light entering the eye by adjusting the size of the pupil. It is composed of muscular fibers that constrict or dilate to regulate light intake, aiding in visual perception.
congrats on reading the definition of iris. now let's actually learn it.
A layer at the back of the eyeball containing cells sensitive to light that trigger nerve impulses that pass via the optic nerve to the brain, where a visual image is formed.