THE RELATIONSHIP BETWEEN MONOCHROMATIC LIGHT AND PUPIL DIAMETER. THE LOW INTENSITY VISIBILITY CURVE AS MEASURED BY PUPILLARY MEASUREMENTS

Abstract

A new infra-red photographic method for measuring pupil diam. under any condition of light adaptation is described. The human dim visibility curve obtained by relating pupil diam. to intensity of different monochromatic lights has its maximum at 510 millimicrons. It is similar in all respects to the classical dim visibility curves and to the absorption spectrum of visual purple. It is therefore believed that the pupil size relative to light stimulation is under the control of fibers activated by the rods of the retina, as well as the cones.