A theoretical study of the effect of silicone oil on the electroretinogram.

A model of the electroretinogram useful for determining volume conductor effects was used to determine quantitatively the postvitrectomy effect of silicone oil on the ERG. The electrical conductivities of the structures of the eye, the frequency content of the ERG, and the percentage of silicone oil along with the remaining vitreous were incorporated in the model. The result was that it was not until at least 50% of the vitreous was replaced with silicone oil that there was a small reduction of the electroretinogram; this reduction increased nonlinearly as the percentage of silicone oil in the vitreal cavity increased. According to the model, if the vitreous replacement were large, little, if any, of the ERG would be measured even if the retina were quite functional.