The classification rules of the International Federation for Equestrian state that athletes with a physical impairment and athletes with a visual impairment are eligible to compete in the sport at the Paralympics.
Classification also groups athletes in classes, defined by the degree to which they are limited in their ability to perform activities within that sport.
There are five classes in Equestrian: Grades Ia, Ib, II, III and IV.
Grade Ia is for athletes whose impairment has the greatest impact on their ability to ride; through to Grade IV, which is for athletes whose impairment has the least impact on their ability to ride.
Read an overview of classification at the London 2012 Paralympic Games