H.E. Henkes

Electro-oculography. A semi-automatic recording procedure.

ELECTRO-OCULOGRAPHY has been established as a valuable clinical procedure for measuring indirectly the standing corneo-fundal potential, of importance in the investigation of retinal and choroidal function. Although the technique of clinical recording is not very complicated, the load of a great many records is a burden for the technical staff of an electro-diagnostic clinic. Semiautomatic recording, using a simple and reliable technique, has proved to be of help in this situation.

PERIODICAL INTEGRATION OF RETINAL RESPONSES FOLLOWING REPETITIVE LIGHT STIMULI. A METHOD FOR THE DEMONSTRATION OF MINOR CHANGES IN RETINAL ACTIVITY

Aiming at the determination of the significancy of minor alterations in the electric activity of the retina, the recording and subsequent electronic integration of the selectively amplified flicker-ERG has some advantages over the recording and elaboration of the single flash response. These advantages are: 1. The elimination of the influence of biologic variations in individual responses. When flickering light stimuli are used, electronic summation of individual responses will greatly minimize, or even eliminate this influence due to the number of individual responses treated per given time unit. Using a stimulus rate of 10 flashes per second, summation of the flicker-ERG over each period of 10 seconds will cover 100 individual responses. 2. Steady state of retinal adaptation. If individual light stimuli are employed, the state of retinal adaptation will vary continuously, as every lightflash will influence the state of dark adaptation. During repetitive stimulation, a steady state of adaptation of the retina is soon reached. 3. The possibility to use light stimuli of low intensity. Under >>normal<< clinical conditions, a reliable recording of individual responses is only possible when the recorded potentials exceed clearly the noise level. The smaller the potential of the individual response, the more difficult and the less reliable the measurement of the individual response will be. (With the exception of averaging methods of integrating the individual responses; up to now, however, asking for a complicated instrumentation e. g. Henkes and van Balen, 1960) This forces US to the use of relatively high intensities of stimuli, which as a consequence may activate at the same time the photopic mechanisms, although we aim at the selective stimulation of the scotopic mechanism. Selective