The best treatment for chronic glaucoma has often been discussed, but even at this time considerable difference of opinion exists in regard to the most satisfactory method, while the prognosis of the disease, depending as it does upon many factors, is always a doubtful quantity even after the most skilfully performed surgical interference. Most surgeons will, I think, subscribe to the doctrine of Dr. Bull, who says, "It seems to be our duty to operate in cases of chronic progressive glaucoma, and the earlier the better." It is presupposed that the patient has previously been warned of the nature of this disease to progress towards blindness and, as Priestley Smith has said, of the uncertainties which beset the operation. When a case of chronic glaucoma is under observation and the surgeon is weighing the chances for and against operation, it becomes necessary not merely to test the acuity of vision,