Just because people lose their sight doesn't mean that they can't read anymore. They just learn to read in a different way.
Blind people read by running their fingers over pages that have groups of tiny raised dots. These dots represent different letters, and they form an alphabet that's just like ours. This writing system is called braille.
Braille has a very interesting history. Its story begins around 1800, when a French soldier named Charles Barbier created a system of raised dots so that soldiers could read messages in the dark. Napoléon wanted his troops to be able to communicate in the dark without giving away their positions. In the end, this so-called "night writing" system was too complicated for soldiers to learn. It had to be rejected by the military.
Years later, Charles Barbier met Louis Braille at the National Institute for the Blind in Paris. Louis Braille had been blind since the age of four, and he immediately ecognized both the potential importance of Barbier's system and its major flaw. Louis set to work on making it easier to use, and eventually the braille system was born.
In braille, each letter, or cell, is made up of a rectangle in which there can be a combination of up to six raised dots or an absence of dots. The six dots are arranged in a grid of two dots horizontally by three dots vertically. The dots are numbered 1, 2, and 3 from top to bottom on the left column and 4, 5, and 6 from top to bottom on the right column. There can be 64 different combinations. Braille has also evolved to accommodate differences in other languages. For example, Greek braille is different from Chinese braille.
Blind people can also write in braille. Most use a special typewriter, called the Perkins Brailler, which types braille onto paper. Nowadays, computer keyboards with braille symbols are also available.
It is amazing that a military technology from the Napoleonic Wars has grown into something that has improved the lives of countless blind people around the world.