| A | B |
|---|
| Retina | Is the thin tissue behind the lens at the back of the eye. This is where the picture of what you are looking at is brought together (upside down). It contians rods and codes. |
| Lens | Allows light to pass through it. |
| Iris | The coloured part of the eye which controls the amount of light that can pass through the lens to the retina. |
| Muscle | In bright light these make the pupils smaller, allowing less light to enter. In dim light, the reverse occurs. |
| Pupil | The dark spot in the eye. It looks dark because you are actually looking into the inside of the eye. |
| Cornea | Is a thin, clear layer over the front of the eye. It protects the eye and brings together light that enters the eye. |
| Rods and Cones | Are nerve cells which react to light. |
| Rods | Make it possible for you to see in dim light. |
| Cones | Allow you to see in bright light and to see colour. |
| # Rods | 125 million (each eye) |
| # Cones | 7 million (each eye) |
| Optic Nerve | Separately connects all the rods and cones to the brain. |
