During childhood, people with normal vision have the ability to focus on objects as close as their nose and also on objects very far away. They can rapidly, without conscious thought, switch focus from near to far vision. This is called accommodation. As each year passes, that ability to focus and to switch focus decreases. By the time most people reach their forties, they need an aid, such as reading glasses or bifocals, to focus on objects close up. This condition is called presbyopia.