In the past eight years somewhat over 3,000 patients have been examined with the electroretinogram in our department. In this period of time there have been two instances of corneal burn due to electrical energy from the recording device being fed into the patient. In neither of these instances was there any permanent damage done, but considerable discomfort on the part of the patient and concern on the part of the examiner was engendered.
In an attempt to eliminate, as much as possible, this type of accident, a study of the possible sources of such technical failures was begun and a search for a means of prevention of repetition. The electrical circuit normally in use for clinical electroretinography is shown in Figure 1A. The patient, who is grounded, is connected by way of a contact-lens electrode to the input of an amplifier. This amplifier develops within it "stray capacities"
JACOBSON JH, GESTRING GF. Prevention of Ocular Trauma During Electroretinography. AMA Arch Ophthalmol. 1959;61(6):941-943. doi:10.1001/archopht.1959.00940090943010