The pains which may occur in acute iridocyclitis are among the most severe to which mankind may be subjected. It is often impossible to control them satisfactorily even with morphine or codeine, and the unfortunate patient must be allowed to suffer some twenty-four to forty-eight hours after vigorous treatment has been instituted.
In acute iridocyclitis the pain is a spasmodic ciliary neuralgia superimposed on a dull ache and is worst in the acute stages, when the tissue is swollen and hyperemic and the nerve endings are stimulated by a high concentration of toxic substances.1 This pain is not confined to the eye but usually radiates over certain divisions of the trigeminal (the fifth) nerve. The malar region and the cheek may be involved, but by far the commonest site of radiation is the brow and the forehead via the supraorbital nerve. This neuralgia-like pain bears no definite relation to