The pupil is situated in the very center of the iris. It represents a black opening through which the light passes while entering the eye. The size of the pupil itself is controlled by contractions and moving of the iris muscle’s perimeter that changes the opening of the pupil and thus regulates the quantity of light in the eye. This is also known as the pupillary reflex.
In the presence of a strong light the pupil decreases to 1,5 mm, while in dimmed light its size increases even to 8 mm. The shape of the pupil itself differs depending on the space of the Iris and ranges from rounded to oval.