In order to see clearly, light from an object has to be focused by the optical elements of the eye onto the retina. The retina is a thin layer, about the thickness of a piece of tissue paper, which is next to the inside wall of the eye.
There are certain parts of the retina that perform different visual tasks. For example the retina towards the front of the eye is best used for detecting objects in the dark. The macula is another small part of the eye which we use for visual tasks such as reading, driving and watching TV. A hole in this part of the retina is called a macular hole.