I have only ever seen blind cricket demonstrated on TV. As I recall they used a ball which contained rattles. However, you would not want to play the regular game if you are blind. I remember a batsman being killed when hit with a cricket ball over the heart.
That's very interesting, thank you. The idea of them using a ball with rattles in it takes a bit away from the amazement that I was feeling but not much...it's still incredibly impressive that they are able to do this.
The type of injury you refer to is known as blunt cardiac trauma, and it is becoming more commonplace (or at least the diagnosis is). It is happening more and more here in the USA in baseball, and can cause a heart arrhythmia, an infarction (heart attack) even in children, or even a torn aorta (blunt aortic trauma) which is frequently fatal.. So it's best to keep your eye on that ball :-)