The effect of a retinal lesion on the distribution of B wave potentials on the sclera

In the experiments presented here we have used the isolated perfused eye technique to investigate the distribution of ERG potentials on the sclera over local retinal lesions induced by xenon arc photocoagulation. Three lesioned dog eyes were examined. In two cases the lesion was allowed 28 days to stabilize, whilst in the third the experiment was performed two hours after treatment. Immediately after enucleation, the eyes were placed in a perfusion system capable of maintaining retinal function for many hours. The scleral ERG profile was then measured on the scleral surface over both treated and untreated areas of retina in the same eye. It was found that the ERG amplitudes were consistently lower over the treated areas of retina when compared to the untreated side of the same eye. More surprising was the discovery that the ERG distribution on the untreated side was significantly different to that observed in control eyes. In particular it was found that the limbal areas of sclera on the untreated side now had significant ERG amplitudes present, whereas the control eyes had close to zero amplitude in this region. It is concluded that the induced retinal lesions caused a widespread redistribution of ERG potentials around the entire surface of the globe. The potential applications of these results in the assessment of local retinal function is discussed. A schematic model is presented for the distribution of ERG potentials on the surface of control and lesioned eyes.