Function of retina: It has light sensitive cells called rods and cones. Cones are responsible for coloured vision and observation when the light is strong. Rods are receptors for seeing in dim light. Retina has cells that convert the light falling on it into chemical signals that go to brain and get interpretted as image.
Function of pupil: It controls the amount of light that enters the eye. It enlarges in dim light and becomes smaller in bright light.
Function of optic nerve: It carries the message of sight from retina to the brain.
