[Inter- and intra individual variations in the EOG]

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.

Normal values in clinical electrooculography. V. Variability within and between eyes

Three EOG's (DC amplified 30-degree saccades, slightly modified Arden schedule) were recorded at weekly intervals from each of 16 normal human eyes (eight subjects). The light induced potential rise of the dark-adapted eye, the Arden ratio and the Gliem ratio entered into the analysis of intra- and inter-eye variation. The 95% confidence intervals for the mean parameter values of each eye were: +/- 59 muV (mean = 415 muV) for the light induced potential rise, +/- 22 (mean = 260) for the Arden ratio and +/- 10 (mean = 92) for the Gliem ratio. The intra-eye variability was compared to earlier studies of the day-to-day variation of the ERG by means of a dimensionless index; no substantial differences were found. Highly significant differences in the EOG parameter levels existed between the subjects, whereas the variation between right eye and left eye means in the individual subjects was ise respects. The primarily qualitative nature of the EOG in the present version is emphasized by the present results.

Normal values in clinical electrooculography. IV. Analysis of two dimensionless EOG parameters and their relation to other variables

Two EOG parameters - The Arden ratio (A) and an expression devised by Gliem (G) - from a sample of normal human subjects are studied. Their relations to the EOG potential and time parameters and to sex, age, pupillary diameter, degree of iris pigmentation, refractive error and axial length, ocular protrusion and interpupillary distance were assessed. Right eye and left eye distributions were congruent, although individual differences were sometimes appreciable, especially in the case of G. The two ratios were positively correlated and both showed a negative correlation to the interval between the dark trough and the light peak. Correlations to the EOG potential parameters, especially the light induced potential rise of the dark adapted eye, were also established. In the case of A, a higher level was disclosed in the male half of the sample. A negative age correlation, predominant in the female part of the sample, characterized both ratios. The two ratios were positively correlated to the pupil diameter, negatively correlated to the degree of refractive errror, and positively correlated to the degree of ocular protrusion. The consequences for the clinical EOG test are discussed, and it is concluded that the present EOG procedure is a qualitative rather than a quantitative test.

Normal values in clinical electrooculography. III. Numerical evaluation of two dimensionless EOG parameters

The distribution of the Arden ratio (A) and another dimensionless EOG quantity (G) devised by Gliem (1971) in a sample of normal human subjects are presented. The minimum, median and maximum values for A are 148--241--449 and for G 34-88-167. A demonstrates a smaller degree of dispersion than G, the latter resembling in this respect the EOG potential parameters of the same sample. The average accumulation of errors due to inaccurate assessment of the included potential figures is almost equal in the functions of A and G. Divergencies between the figures from the present and earlier investigations are discussed together with the general advantage of dimensionless EOG parameters. It is concluded that the present investigation has not demonstrated the need to replace or supplement the Arden ratio by the Gliem quantity.

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.

Normal values in clinical electrooculography. 1. Material, method, methodological investigations and distribution of the potential and time parameters

For the evaluation of normal EOG potential and time parameters a case series (142 eyes) is presented. An EOG technique aiming at the largest possible amplitude between the dark trough and the light peak is described. It is shown that the light-induced response following a 20 min period of adaptation to a very low degree of illumination (about 1/10 lx, allowing a rough orientation on the displayed trace) does not differ from that produced after 20 min of total darkness. Also, the independence of the pupillary area for the light-induced response is demonstrated, which means that the light stimulus employed (2500-4000 lx) is supramaximal. Furthermore, the good quality of the gaze fixation in the actual test situation with respect to the recording of equidistant saccades is proven. A DC amplification of the signal is used, which secures independency of inter- and intra-individual differences in the saccadic velocity and makes possible accurate measurements of deflections disfigured by correcting movements. The following EOG parameters are recorded: A base value after 10 min of preadaptation with the light stimulus, the dark trough and the light peak potentials. Also the periods between the beginning of the dark adaptation and the dark trough and between the dark trough and the light peak are noted. The frequency distribution and the general level of the various parameters are discussed in the light of comparable figures of previous publications.

[The influence of the eye prominence on the EOG potential level (author's transl)]

The influence of globe prominence on the electro-oculogram potential level was measured in patients with unilateral protrusio bulbi, myopia or hyperopia. The EOG potential level on the side with the more prominent globe was lower if the prominence was due to protrusion. If the prominence was due to myopia, the EOG potential was higher compared to the contralateral non-myopic eye. In hyperopic eyes the potential level was lower.