COMPARATIVE STUDIES ON THE PERIPHERAL AND CENTRAL RETINA

Abstract

In order to obtain information as to whether there is any interaction between distant areas in the human eye, the fusion frequency of 4 circular test patches, separated by an un-stimulated area, was measured for each of the patches in turn and for all of them together. The 4 stimuli, each of a diameter of 1[degree] of visual angle, were placed symmetrically with their outer edges on an imaginary circle, the diameter of which was either 3[degree] (arrangement I) or 4[degree] (arrangement II) of visual angle. The test patches were illuminated at 2 different intensities, the one 100 times lower than the other. The fixation point was either in the center between the stimuli or 10[degree] out towards the periphery. With central fixation and the higher intensity there is very little interaction between the stimuli in arrangement I, as shown by the fact that the fusion frequency of all the patches illuminated together is only about 0.25 of a revolution per sec. higher than the corresponding value for each of them viewed in turn. With the weaker intensity there is no interaction at all. With peripheral fixation under similar conditions there is an increase in the fusion frequency of about 2.5 revolutions per sec. for all the patches together over the value obtained with the single stimuli. The interaction is definite still with arrangement II where the patches are further apart, the fusion frequency for all of them together being about 1.6 revolutions per sec. higher than the average for the singles. Even if the intensity of the stimuli is diminished 100 times there are still definite signs of interaction left. The results prove the existence of physiological irradiation in the human eye and thereby give a definite solution of an old problem of vision. The difference between central and peripheral vision with regard to interaction is correlated with corresponding structural differences in the 2 parts of the retina. The general agreement between the outcome of the experiments recorded above and recent work on interaction in motor and sensory neurones is pointed out.