Louis Braille's father, Simon-René Braille, was a harness/saddle maker, and at the age of three Louis injured his left eye with an awl from the workshop. This caused an infection in his left eye which also infected his right eye and he became blind. When he was ten he earned a scholarship to the Royal Institution for Blind Youth in Paris. At the school, the children were taught to read by feeling raised letters but they couldn't write because the printing was made with wire letters pressed onto paper. At the age thirteen he invented the raised dot system with inspiration from the retired army captain Charles Barbier de la Serre who visited the school, bringing with him a system created so soldiers could pass orders silently at night. Serre's system was based on twelve dots, whereas Braille's is based on six dots. Braille later extended his system to include notation for mathematics and music.