pupil – the hole in the centre of the iris that allows light to enter the eye

(Pronounced pyoo-pl)

To remember the meaning of pupil, use the following mnemonic:

The pupil (pupil) drilled holes into his iPad (eye).

The pupil is the circular opening in the centre of the iris (coloured part of the eye) that controls the amount of light entering the eye. It appears as a black hole because light entering through it is absorbed by tissue inside the eye rather than being reflected back. Muscles in the iris enable the pupil to grow larger (dilate) in low light conditions (to let more light in) and contract (constriction) in bright conditions (to reduce light entering the eye). This automatic adjustment of pupil size protects the retina within from being damaged, while also allowing better vision in he dark. The pupil also constricts when focusing on near objects and dilates when looking at distant objects, which helps improve depth of vision.