CHANGES IN THE CAT ERG AND IN THE ERG INTENSITY FUNCTION AFTER CHRONIC REPLACEMENT OF THE VITREOUS BODY BY SILICONE OIL

1. In 19 anaesthetized adult cats the flash electroretinogram (ERG) wa s measured before and after the vitreous body was replaced by silicone oil. 2. After several months the silicone oil caused a significant re duction in the b-wave amplitude of the ERG and a corresponding change in the b-wave intensity function. The averaged time constant of the ex ponential decay in ERG responses was about 160 days. Other parameters of the b-wave like peak latency, b-wave shape and the stimulus intensi ty at which-the b-wave amplitude reached 50% of the plateau value were not significantly changed during the months after vitrectomy. 3. Vitr ectomy and replacement of the vitreous body with Ringer-solution had n o significant effect on ERG responses. 4. The decrease in the flash ER G after vitrectomy and replacement of the vitreous body by silicone oi l is presumably caused by a slowly progressing retinopathy, which may be due to impairment of the cellular structures-in particular the cell membranes of retinal tissue-by the silicone oil or by toxic byproduct s of the silicone oil such as heavy metals.