The effect of disease of neighboring parts is also taken into consideration. Whether sympathetic ophthalmia be due to germs or to toxins is still an open question. But just as an eye artificially irritated may become infected with pathogenic germs from some distant focus of infection in the body, so when an injured eye causes a vaso-motor excitation in the other eye, this second eye may become infected equally well by an infective agent from the first eye, as by one from some other portion of the body. If infection does not take place, there is only a sympathetic neurosis.
A look at the past. . .. Arch Ophthalmol. 1999;117(5):642. doi:10.1001/archopht.117.5.642