Electrical stimulation of the palpebral conjunctiva of normal subjects was achieved using gold ribbon electrodes imbedded in scleral lenses. Various electronic parameters and electrode configurations were altered to find the most efficient combination necessary to produce full lid closure. The impedance found for transconjunctival stimulation was one tenth that of percutaneous stimulation. Frequency of stimulation below 25 pulses per second (pps) was painful. Threshold current necessary for full lid closure via transconjunctival stimulation was similar to percutaneous stimulation. Transconjunctival stimulation avoids phosphene induction but does produce elevation of the globe. Finally, transconjunctival-stimulating currents of greater than 100 pps produced lid anesthesia.
Miller D, Kohn A, Weiss AD. Transconjunctival Stimulation of the Musculus Orbicularis. Arch Ophthalmol. 1973;90(5):389-392. doi:10.1001/archopht.1973.01000050391012