Biomedical subjects

K J Eriksen

Publications and source records attributed to K J Eriksen.

6 recordsLinked to original sources

PubMed1986

Recording pattern visual evoked potentials under chloral hydrate sedation.

Accurate assessment of visual function in infants and preverbal children is difficult because of the dependence on vision tests that require the patient's cooperation. In an attempt to resolve this problem, we evaluated pattern visual evoked potentials (PVEPs) obtained on infants under chloral hydrate sedation. Ten patients were studied--four with unilateral amblyopia, three with suspected amblyopia, and three without amblyopia. Patients with amblyopia showed robust and reproducible responses from the sound eye, while responses from the amblyopic eye were significantly diminished (amplitude ratio less than or equal to 0.63). The PVEP responses from patients without amblyopia were large in amplitude and symmetrical between fellow eyes (amplitude ratio greater than 0.9). In two eyes with normal vision, optically fogging the patterned stimulus image substantially reduced the PVEP response, establishing a sensitivity to pattern images rather than changes in the overall luminance. We have thus determined that the PVEP can be reliably obtained under chloral hydrate sedation and that these responses, like PVEP responses taken in the awake state, reflect the presence of amblyopia and image clarity. Use of the PVEP with chloral hydrate sedation may prove clinically useful for detecting amblyopia in uncooperative infants and children.

Amblyopia↗

PubMed1986

P100 amplitude variability of the pattern visual evoked potential.

This study quantifies the amplitude variability of the pattern visual evoked potential (P-VEP) and compares this variability between the two eyes and between individual runs recorded in the typical clinical laboratory. Cooperative adults were studied in order to obtain measurements under optimal conditions. Average P100 amplitudes of 10 runs for one eye were essentially equal to average P100 amplitudes of the other eye, as were the variances. Mean amplitude ratio (the smaller amplitude divided by the larger amplitude) was 0.91. With a group mean P100 amplitude of 10.06 microV, standard deviation for intrasubject data was 1.84, and for intersubject data was 3.75. Therefore, most of the amplitude variability between the two eyes is due to run-to-run variability. A minimum of 3 runs (100 stimuli each) and an optimum of 5 runs should be recorded before making an evaluation.

Adult↗

PubMedDate not supplied

Suppression and the pattern visual evoked potential.

We assessed the effect of amblyopic suppression on the pattern visual evoked potential (P-VEP). Since anisometropic amblyopia is associated with the monofixation syndrome and a central suppression scotoma in the amblyopic eye, patients with this functional defect were used for the study. Five anisometropic amblyopes and four normal subjects were studied using the P-VEP test. A modified haploscope was used to present a pattern stimulus to the area of suppression. By comparing responses generated under monocular conditions (non-suppression) with monocular responses under binocular viewing conditions (suppression), we measured the effect of suppression on the P-VEP. Our results show that amblyopic suppression completely abolishes P-1 amplitudes in patients with large suppression scotomas; in patients with small suppression scotomas the P-1 amplitudes were greatly reduced. Rivalry in normals also caused a reduction in P-1 amplitudes, but to a much lesser degree than that associated with anisometropic suppression. Patients with significant amblyopia did not show a rivalry effect on the P-VEP. Because the P-1 wave of the transient P-VEP is thought to represent activity at the level of the striate cortex, our results indicate that suppression probably occurs at the striate cortex or lateral geniculate nucleus.

Amblyopia↗

PubMedDate not supplied

Detection of amblyopia with P-VEP during chloral hydrate sedation.

A major limitation of methods presently used for detecting amblyopia in preverbal children and infants is their dependence on patient cooperation. In response to this problem, we have introduced the use of chloral hydrate sedation as a means of obtaining the pattern visual evoked potential (P-VEP) in uncooperative infants. Twenty-five infants were studied: 14 with clinically diagnosed amblyopia, four with questionable amblyopia, and seven with no clinical sign of amblyopia. In patients with known amblyopia, P-1 amplitudes from the amblyopic eye were greatly diminished when compared with responses obtained from the non-amblyopic fellow eye, with amplitude ratios ranging from 0 to 0.66 (mean 0.36). In contrast, P-1 responses from non-amblyopic infants were quite symmetrical, with amplitude ratios of 0.82 to 0.98 (mean 0.92). These results indicate that the P-VEP can be obtained during chloral hydrate sedation and that P-1 responses reflect the presence or absence of amblyopia. Performing P-VEP during chloral hydrate sedation thus holds promise as an important clinical tool for the diagnosis of amblyopia in uncooperative infants and children.

Amblyopia↗

PubMedDate not supplied

Superimposition of a cartoon program as an aid in recording pattern visual evoked potentials in children.

Superimposition of a television program onto the black and white checkerboard stimulus used in performing the pattern visual evoked potential (P-VEP) has been found useful in testing adults and children. This study tested normal-vision children under two conditions: with the cartoon superimposition and with the standard black and white checkerboard. P100 amplitudes were decreased slightly with the superimposition, but the variability was not significantly different. Waveforms and latencies were not altered by the addition of the cartoon. The use of cartoon superimposition therefore can be helpful in maintaining attention during P-VEP testing in children, as long as the diminished amplitude characteristic is taken into account.

Caricatures as Topic↗

PubMedDate not supplied

PVEP evidence of true suppression in adult onset strabismus.

Customarily, it is taught that strabismus acquired in childhood results in suppression of the diplopic image, whereas strabismus acquired in adulthood causes diplopia or conscious image ignoring, but not true cortical suppression. The pattern visual evoked potential (PVEP) was recorded from strabismic patients, three with childhood onset, two adult onset with diplopia, and three with longstanding adult onset strabismus "ignored" diplopia. Patients with childhood onset and adult onset "ignored" diplopia similarly showed essentially no response under haploscopic stimulation, whereas patients with diplopia and normal control subjects showed a 50% decrease (rivalry). These results suggest that adults with acquired strabismus who "ignore" the diplopic image actually have a suppressed cortical visual activity, as evidenced by the pattern visual evoked potential.

Adolescent↗