The effect of voltage and time of application on the electrical impedance of ocular tissues was studied during surface diathermy on pigmented rabbits. During the application, the resistive and capacitive components of the impedance dropped due to an increase in the temperature of the tissues. This drop increased with the voltage applied and contributed to heat the tissues to a much greater extent than would be expected. After diathermy application, a new impedance measurement at the application site gave a higher value, indicating drier tissue and so-called crust formation. This crust increased with the voltage. In order to produce the same degree of chorioretinal burn, the electrical power required was higher for shorter times of application resulting in more destruction of sclera. However, the spread of heat in sclera is lessened with shorter application times.
deGuillebon HF, Elzeneiny I. Electrical Impedance of Ocular Coats During Diathermy ApplicationsVoltage and Time of Application. Arch Ophthalmol. 1970;83(4):489-503. doi:10.1001/archopht.1970.00990030489018