Trachoma is a bacterial infection. It spreads from person to person through eye, nose and throat secretions, especially in areas where there are water shortages, numerous flies, and crowded living conditions. Infection often begins during infancy or childhood and can become chronic. If left untreated, the infection eventually causes the eyelid to turn inwards, which in turn causes the eyelashes to rub on the eyeball, resulting in intense pain and scarring of the front of the eye. This ultimately leads to irreversible blindness, typically at between 30 and 40 years of age.