The retina of the eye contains 130 million light detectors, each consisting of a cone and rod. These connect to nerves that transmit light signals to the brain down the optic nerve. If disease or a blow to the head causes the retina to become detached from the back of the eye, these light signals to the brain become interrupted and sight will be affected. Boxers suffer repeated and violent blows to the head. Detached and torn retinas are a particular problem for them.
Modern treatment of a torn retina involves essentially welding the torn ends of the retina together and to the underlying tissue with a laser. Laser surgery has the advantage of being non invasive and laser beams can be very finely focused onto small spots for very brief periods of time, meaning this sort of treatment can be used in the central part of the retina used for seeing small detail.