Abstract: This disclosure relates to an instrument for use in taking ocular tension measurements by the tonometric method of ocular depression which instrument may be called a tonoscope. The tension measurements, per se, may be made with a tonometer such as Schiotz's tonometer. The tonoscope is provided with, a head piece which may be attached to the patients forehead just above the eyes, a cone adjustably attached to the headpiece to project in front of the right or left eye of the patient and, preferably, an adjustable shade which is movable to temporarily extend in front of the eye on which the pressure is to be measured. Preferably, also, the adjustable cone contains a scale cooperating with a pointer on the headpiece to indicate the angle to which the axis of the cone projects.