1959 Volume 69 Issue 2-3 Pages 103-112
Using, as an index of excitation, the electrical phosphene elicited by the exponentially increasing current running through the eyeballs, the relation of the electric threshold and accommodation in the human retina to brightness discrimination was studied systematically with the eyes adapted to monochromatic rays of varying wavelengths.
1. All of the accommodation curves obtained were of duplex nature, being divided into two sections by an inflexion at about 50-80 msec. in RC.
2. Hill's λ-log-radiance (I) curves were obtained separately for both cases of the time-constants (RC) shorter and longer than 50 msec. Both families of the curves for both cases of RC, were different not only in shape but also in arrangement order of the curves depending on the wavelength of the adapting light.
3. Hill's λ has a parallel relation to spectral luminosity of the adapting light, when the adaptng colored light was of equal energy.
4. It was found that the electric threshold (V) can be expressed by a simple formula as a function of the Weber fraction (W) in brightness discrimination and the intensity (I) of the adapting light, as follows,
V=A (log WP+log I)+B,
where A and B are constants and p is the parameter which relates to the time-constant of the stimulating current.
5. The relation between the accommodation constant (Hill's λ) and the intensity of the adapting light, was deduced mathematically from the formula stated above, and it was indicated that the Hill's λ is inversely proportional to the Weber fraction in brightness discrimination.