The classification rules of the International Federation for Judo state that 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.

Three classes of athletes compete in Judo: B1, B2 and B3.

B1 athletes are classed as blind, while B2 and B3 athletes have different degrees of visual impairment. All athletes compete together.

B1 athletes have a red circle sewn on to the sleeves of their judogi (judo suits). This is in order for the officials to apply the rules according to their special circumstances.

For example, the officials will not expect them to recognise the edge of the contest area, compared with Judo athletes with limited sight. 

When an athlete is also deaf as well as visually impaired, a small blue circle will be attached on the back of the judogi. 

Read an overview of classification at the London 2012 Paralympic Games