A method for DC-ERG recording of alert humans

C-wave versus electrooculogram in diseases of the retinal pigment epithelium

The c-wave and the electrooculogram (EOG) are retinal potentials predominantly generated by the pigment epithelium. In most diseases both parameters show a parallel decrease in amplitude. However, in patients with dominant drusen, and cone dystrophies, and in clinically nonaffected members of families suffering from vitelliform macula degeneration, the EOG is close to normal whereas the c-wave shows a reduced amplitude. These findings suggest a higher sensitivity of the generators of the c-wave compared with those responsible for the EOG. Thus the direct current electroretinogram provides additional diagnostic information.

Changes in corneal DC-potentials associated with changes in pupillary diameter

Using light-emitting diodes we stimulated monocularly with light intensities of between 7.5 and 1,800 cd/m2, and recorded simultaneously the Dc-electroretinogram and pupillary movements of the stimulated and the contralateral eye. In some investigations, the visual evoked potential and the activity from the periorbicular muscles were also recorded. Various drugs acting on the autonomous nervous system were topically applied and their efforts studied. In the eye with an untreated pupil, stimulated or contralateral, a corneo positive potential coincident with pupillary constriction was seen (cu-wave), provided the pupil was large beforehand, a corneonegative deflection dominated, which was also coincident with pupillary constriction (mu-wave). Parasympathicolytics or -mimetics abolished both the cu and mu-wave. We conclude that the cu-wave is related to depolarization of the sphincter pupillae during constriction, whereas the mu-wave might be related to a modification of the potential distribution between the pigment epithelium and the tissue surrounding the eye in the case where the pupil is constricted beyond a critical point.

Course of disturbance of EOG in retinal vessel occlusions

More than 60 patients with retinal vessel occlusions were examined using the electro-oculogram (EOG) ramp test. In the course of the disease a systematic disturbance of the slow oscillation of the corneoretinal potential occurred. First, the latency of the light peak increased. Then the peak decreased and was reached up to 5 min later than in the healthy eye. In the final stage the basic level dropped to about half of the normal value and light response was absent. During the next few weeks an improvement in the basic level took place, but usually this did not involve improved vision.

Intraretinal recordings of slow electrical responses to steady illumination in monkey: isolation of receptor responses and the origin of the light peak

The onset of steady illumination of the mammalian retina initiates a series of complex electrical responses. Corneal recordings in man show a relatively fast ERG, followed by a much slower "light response": a "light peak" followed by a series of damped slow oscillations that may last for 1 or 2 hr. The latter oscillations are a prominent feature of the EOG. We recorded the response to steady illumination with micro electrodes in the intact rhesus monkey eye. The intraretinal "light response" was analyzed by simultaneous recordings at different depths, using a bipolar microelectrode. We found that a steady photoreceptor component can be isolated by fractional recording across the cone outer segment layer in the fovea. Further, through simultaneous recordings at the retinal and choroidal sides of the retinal pigment epithelium, we found that this structure is most probably the generating site of the "light peak" and subsequent oscillations of the standing potential.

Examination of the fast oscillation of the corneoretinal potential under clinical conditions

The "fast oscillation" of the corneoretinal potential can be precisely examined by means of cyclic light stimuli and an automatic measuring device. This new procedure is carried out during the period of adaptation as part of the usual EOG-test. Normal values and some clinical findings are presented. The fast oscillation may provide additional information when compared with EOG and ERG results.

The registration of slow ERG potentials of the perfused extracorporeal bull's eye

Enucleated bull's eyes were perfused with blood and ERG recorded, with special attention paid to the slow components. When the blood flow was interrupted, the ERG components vanished in the following order: b wave, c wave, off-effect (d wave), and a wave. When the perfusion was continued afterward, we saw a variation in the standing potential that hinted at the biochemical activities causing slow electrical potentials of the retina.

EOG: light test and dark test

The EOG test is divided into two parts: a light and a dark test. The adaptation period is extended to 30 min. During this adaptation period the luminance in the cabin decreases (or increases) slowly to the starting value of the light or dark step. In a model, we studied the influence of this ramplike luminance course on the results. Standard values for the test were calculated with 30 test persons. Our test results show a lower relative standard deviation (V = 10%) compared with earlier published results.

ERG of humans without C-wave

Three out of 18 healthy persons investigated with the DC-ERG do not show a c-wave. By varying the adaptation levels and intensities of the stimuli four components in the human ERG can be isolated, the cone and rod late receptor potentials, the positive DC response, and a c-wave in most subjects. It is suggested that investigation of these components reveals a more detailed understanding of the pathophysiologic mechanisms in some retinal diseases.