Quantitative analysis of the insulating effect of silicone oil on the electroretinogram.

A model of the ERG focusing on the insulation effect of silicone oil replacing the vitreous was used to quantify the ERG. The electrical properties of the structures of the eye, the frequency content of the ERG and the percentage of the silicone oil along with the remaining vitreous were incorporated in the model. The result was that it was not until at least 50 per cent of the vitreous was replaced with silicone oil that there was a small reduction in the ERG. As more silicone oil was put into the vitreous cavity the ERG became smaller. If the replacement were large leaving a layer of vitreous 0.24 mm thick, little ERG would be measured even if the retina were functional.