Attention turned to electrical stimulation because it was noted that some patients who had a retinal prosthesis (see Artificial Vision) experienced small improvements in their vision even when the device was switched off.
In theory, trans-corneal electrical stimulation (TES), undertaken with corneal electrodes, might protect dying retinal cells and improve retinal function, although as yet there is very limited evidence to support this theory. So far electrical stimulation has only been trialled in a few small studies in patients so the risks and possible benefits have yet to be determined.