Contrôle objectif de la conductibilité des voies optiques centrales par l’électro-rétinographie et l’électro-encéphalographie combinées

Abstract

Simultaneous electroretino- and electroencephalograms are taken with the subject in sitting position facing the perimeter, this latter equipped with the device of light stimulation. The con-junctival electrodes are fixed on a spectacle and the others on the skin. This method enables one to decompose the a-rhythm into 2 periods. The duration of the first (retinal time) extends from the onset of the light stimulation to the moment the impulses are discharged into the optic nerve; it corresponds to the latent period of potential b of the electro-retinogram and varies with stimulation intensity. The authors measured the retinal latent period and obtained 45 msec. in the normal subject. The 2d period (post retinal or central time) lasts 124 msec. in the normal subject. It corresponds to the conduction time of the impulses within the central optic tract and is independent of stimulation intensity. In a case of tabetic atrophy of the optic nerve, a longer conduction time (229 msec. right and 264 msec. left side) was found. This central time was also subject to greater variations than in the healthy.