[Impulse electrooculography--a new objective method of clinical electrooculography].
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Eye-movement recordings may be helpful in the differentiation of Duane's syndrome from sixth-cranial-nerve palsy. Voluntary horizontal saccades were recorded and quantitated by electrooculography in 18 patients with unilateral type I Duane's syndrome and in 25 patients with sixth-nerve palsy. When ranges of abduction were matched, the peak velocities of abducting saccades in affected eyes were decreased equally in both groups. However, the peak velocities of adducting saccades in sound eyes were slowed in patients with Duane's syndrome. Because the standard deviations in saccadic velocities are large, computer-based, stepwise discriminant analyses were performed to identify the variables that proved to be useful in differentiating the two disorders. By entering these variables into the discriminant functions that were created, we could distinguish Duane's syndrome from sixth-nerve palsy in a statistically significant manner.
Electrooculography and study of contrast sensitivity allow us to explain by the trouble of pursuit or saccadic movements the inability of some subjects to read or work. Presentation of clinical cases of pursuit inability or of trouble of contrast sensitivity.
In a series of asymptomatic patients with primary biliary cirrhosis there was a significant impairment of dark adaptation thresholds as compared with a control group. Vitamin A levels were abnormally low in only two of the patients and these two both showed high dark adaptation thresholds. The electrooculogram was reduced in only the most severely affected case. It is suggested that visual function tests should be performed alongside vitamin A level measurements before deciding on treatment.
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The electro-oculogram (EOG) is recorded by a personal computer and analyzed during the examination. If the results obtained with this method in normal subjects are compared with the conventional method (with which data recorded in analog form have to be measured manually), there is no significant difference. In patients with diseases of the posterior segment (e.g., posterior uveitis) or intraocular foreign bodies the results of computer and manual analysis are also practically identical. There are two computer analysis techniques: for subjects with almost normal EOGs the trigger-independent method is sufficiently accurate. In patients with pathologic EOGs, however, and in particular those with small potential differences, the trigger-related method is more likely to lead to correct results. The analysis path can be displayed on the computer monitor at any time, so that the examiner can always check whether it is correct. In contrast to manual analysis, the computer analysis cannot be influenced subjectively by the examiner. This considerably improves the comparability of examination results. A further advantage of computer analysis is its speed: the result is available immediately following the examination. It is a low-cost system which is easy to install and use, and thus suitable for routine clinical work.
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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 following EOG potential and time parameters from 72 normal subjects were analysed: base value B, dark trough D, light peak L, light induced potential rise L-D, interval between beginning of dark adaptation and occurrence of dark through d and interval between dark trough and light peak l. Their relations to sex, age pupillary diameter, degree of iris pigmentation, refractive error, axial length, corneal curvature and diameter, ocular protrusion and interpupillary distance were assessed. Right eye and left eye samples of the EOG parameters were congruent, although individual differences were sometimes appreciable. The levels of B and D were higher in the female half of the sample. A positive correlation existed between age and D level. L-D was negatively correlated to the degree of refractive error and positively correlated to the ocular protrusion. A positive correlation was found between d and the four potential parameters, and there was a positive correlation between age and l. Practical consequences of the statistical analysis relating to the interpretation of such EOG data are discussed.
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.
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.
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.
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A simultaneous blind study of posture and eye movements was undertaken in 9 subjects at risk for Huntington's disease. After quantitative evaluation of the postural and electrooculographic abnormalities, the subjects were subdivided into subgroups, and the results were compared to test the relationship between the two methods. There was a significant correlation between the two evaluations. 5 of the 9 patients had evaluation scores which reflected abnormalities similar to those observed in patients suffering from Huntington's disease. These preliminary results suggest that posture and eye movement recordings could be tested for their predictive value in Huntington's disease.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.