Three-dimensional electromagnetic model of the human eye: advances towardsthe optimisation of electroretinographic signal detection

Classical electromagnetic theory is used to examine the topographical varia tion in electrical potentials over the corneal surface resulting from speci fic retinal stimuli. Results from a three-dimensional mathematical model sh ow that over 97% of calculated electromagnetic field potentials lie within 3% of previous analytical model data for an axially symmetric case. Maps of corneal potentials are produced that are shown to be characteristic of spe cific retinal stimuli and location. The maximum variation in corneal potent ial for a full field global stimulus is found to be approximately 1%. This is considered encouraging, as current electrophysiology techniques measure ocular potentials from a single corneal or scleral site, the position of wh ich is often difficult to localise and reproduce. The model is used to simu late both central and peripheral stimuli and scotoma conditions. A 20 degre es central scotoma simulation shows an overall reduction in central corneal potential of only 3%, whereas peripheral stimuli are found to cause up to 10% variations in this potential. There is therefore a possibility that a s ingle recording site for multifocal retinal stimulation is not ideal. These data may be used to suggest more appropriate electrode recording positions for maximum signal recovery, not least in optimising signal detection for multi-focal electroretinography stimulation.