FLICKER AND STABILISED RETINAL IMAGE

The percentage of time (V) for which a sinusoidally flickered stabilised retinal image is visible, was measured for frequencies in the range 0-25 c/s, and in relation to several parameters. It was found that V reaches a maximum at a certain frequency, fp, and decreases fairly rapidly for frequencies either side. For a 1.5° bipartite field, located on the fovea, flicker has an overall positive effect on V, and fp is around 5 c/s for all colours except blue, which gives anomalous results. The value of fp decreases with decreasing luminance, with increasing field size, or as a small field is moved to the parafovea. Variations of contrast, or blurring the field, have no effect on fp although V is affected. If square-wave or highly modulated flicker is used, non-linear effects become pronounced and fp depends on colour. The results are discussed in relation to the increase in size of retinal receptive fields with distance from the fovea, and in relation to the pseudo-resonance" ideas of de Lange and Kelly. © 1968."