Laryngostroboscopy in the Practice of Otolaryngology

PHYSICAL BASIS OF STROBOSCOPY Stroboscopy is based on the following facts of physiologic optics: A light impression impinging on the retina will be retained for a longer time than the time of presentation of the object whence that light impression comes; that is, the effect of retinal stimulation will continue after the physical stimulation proper has ceased. This effect is called the positive after-image. The interval between the successive retinal stimulations is such that each stimulation merges with the still present effect of the preceding one. The minimal interval at which this occurs has been variously estimated as from one fifth to one seventh of a second; that is, when two stimulations follow each other at an interval of less than from one fifth to one seventh of a second, separate stimulations recognizable as distinct from each other are no longer sensed. The observation of a luminous body through