Dark-adaptation with especial reference to the problems of night flying.

This work was undertaken with a view to designing a method whereby the visual fitness of the aviator for nightflying might be tested.His absolute sensitiveness for light is one datum sought.Another is his rate of recovery after the relative blinding following exposure to light for short periods.Researches heretofore made on dark-adaptation have shown that in the course of an hour spent in the dark the sensitiveness of vision for light increases gradually, and may in the course of the hour increase several thousandfold over its initial value; 1 or less according to the duration and the intensity of the light to which the eyes have been previously exposed; 2 until a point is reached beyond which no further change is to be found.The present work contemplated exposing the eyes of the observer to light of a standard intensity for certain measured periods of time, and subsequently investigating the course of his light sensitivity.Since from what has just been said it appears that exposure of the eyes to light prior to the time the observer comes under investigation may produce effects which do not completely wear off in less than an hour, it was necessary, before beginning the experiment proper, to make sure that the observer had reached a standard and reproduc-1 Piper, 'Ueber Dunkeladaptation,' Zritsch.