Time course of brightness under transient glare condition.

It was shown that a peripheral glare source reduces the brightness of a foveal stimulus. We hypothesized that this brightness reduction is governed by an inhibitory effect of the glare source on the test. We reported the results of an investigation of the dynamic of brightness reduction of an incremental stimulus immediately after the onset of a glare source in the field of view. A magnitude comparison paradigm using constant stimuli was adopted to determine the luminance that appeared equal in brightness to the standard patch. The luminance of the standard stimulus was in the mesopic range (0.5 cd/m2), and the levels of glare were 15 and 60 lx. Results showed that the time course of brightness reduction followed the typical shape attributed to the Broca-Sulzer effect. Data were fitted with a model that first considers the response of a peripheral ganglion cell to glare and then its inhibitory effect on the test signals. We discussed the plausibility of a postretinal stage of processing.