In making a diagnosis of intracranial tumor the physician seeks for evidence of what is known as choking of the optic disks. It is not necessary to explain the meaning of this term. Neither is it necessary to go into details concerning the cause of choking of the optic disks. Suffice it to say that the evidence favors the view that it is due to obstruction of the return flow of blood from, perhaps also lymphatic drainage of, the retina. This may be due either to local obstruction along the course of the optic nerve or to a general increase in the intracranial tension. If the ophthalmologist could always be certain of the diagnosis of choking of the optic disks and if this finding were produced only by intracranial tumor, it would be very helpful. Unfortunately other conditions of the retina may simulate choking of the optic disks, and