Completar frases Unit 3. Human interaction and health II. The sense of sight.Versión en línea We are going to review what have we learnt about the sight, its elements and its functions. por Daniel de la Cruz Manjón Pozas 1 amount expands iris contracts centre pupil front Light ? The is at the of the eyeball . enters the eye through the , a small hole in the of the iris . The pupil and depending on the of light it receives . 2 iris shape lens focus ? Behind the , there is a flexible . The lens changes to the image . 3 brain optic stimulus receptor signals eyeball retina ? The , at the back of the , contains the cells . They capture the and send along the nerve to the .