Abstract
This paper gives the results of the experiments made at the research laboratory of the Tokyo Electric Co. as to the effect of illumination upon two phases of ocular functions, visual acuity and speed of vision. Illumination is measured on brightness basis. In discussing the results König's and Ferree-Rand's data are referred to and the following points emphasised.
1. König's classical formula is found to make the results interpretable.
2. The maximum point of visual acuity is reached at the brightness of not less than 25 millilamberts.
3. As the standard field brightness for clinical tests of visual acuity 10 millilamberts is recommended.
4. Schwarzschild's law bids fair to hold for the sensitometrical data of retina.
