Electro-Oculographic Studies in Rabbits Treated by Retino-Toxic Agents

ABSTRACT

The influence of sodium iodate and sodium iodoacetate on the standing potential of rabbits' eyes were investigated with the use of electro-oculography. The electro-oculogram was recorded 1, 3, 5, 24 hours and 5 days after the administrations of the drugs. In order to measure the potential changes induced by illumination, animals were maintained in the dark for 30 minutes and thereafter in the light(illumination 500 lux) for another 30 minutes, during which records were taken every two minutes. In normal eyes, the potential decreased during dark adaptation, and its maximum decrease(about 35%) was attained about 24 minutes. When the eye was exposed to illumination, potential increased, the maximum increase (30%) occurred at 18 minutes. Light peak-dark trough ratio was over 1.4 in all eyes and 1.6 on the average. When the dark-adapted retina was illuminated, EOG amplitude showed a rapid, transient rise followed by a slight fall, with the subsequent light rise. After administration of sodium iodate(20mg./kg.) fall of potential during dark adaptation and rise during light adaptation decreased in its magnitude, accompanied by shortening of dark trough time and light peak time. The light peak-dark trough ratio showed moderate diminution (between 1.2 and 1.3). At the beginning of light adaptation, potential fell transiently followed by continuous slow rise. In eyes treated by sodium iodoacetate (20mg./kg.) potential alterations due to illumination diminished as in eyes treated with sodium iodate. The base-value remained almost unchanged. From these observation, it became clear that the standing potential originated mainly from pigment epithelium, and that the presence of intact visual cells was responsible for alterations induced by level of illumination.