Biomedical subjects

E Bo Yang

Publications and source records attributed to E Bo Yang.

3 recordsLinked to original sources

PubMed2006

Multifocal visual-evoked potential in unilateral compressive optic neuropathy.

AIM: To evaluate the effects of unilateral compressive optic neuropathy on amplitude and latency of multifocal visual evoked potentials (mfVEPs). METHODS: Static automated perimetry and mfVEP recordings were obtained from six patients with presumed meningiomas affecting one optic nerve. Monocular and interocular amplitude and latency analyses were performed and compared with normal control subjects. RESULTS: The change in the mfVEP amplitude agreed with visual field findings with regard to topography and severity of deviation from normal. The delay in recordable responses from affected eyes ranged from 7.6 to 20.7 ms (interocular analysis) and 7.9 to 13.9 ms (monocular analysis). CONCLUSIONS: Compressive optic neuropathy decreases the amplitude and increases the latency of the mfVEP. The changes in latency were similar to those seen in optic neuritis but larger than those in ischaemic optic neuropathy and glaucoma.

Aged↗

PubMed2004

Determining abnormal interocular latencies of multifocal visual evoked potentials.

PURPOSE: To describe methods for measuring interocular latency differences of multifocal visual evoked potentials (mfVEP) and for determining regions with abnormal interocular latencies in patients. METHODS: The mfVEPs from 100 individuals with normal visual fields and normal fundus examinations were analyzed. Individuals ranged in age from 21.6 to 92.4 years. The stimulus was a 60 sector, pattern-reversing dartboard display. Each sector had 16 checks, 8 white (200 cd/m2) and 8 black (< 1 cd/m2). Interocular latency was measured as the temporal shift producing the best cross-correlation value between the corresponding responses of each eye. The 'corrected interocular latency' was defined as the difference between this shift and the mean interocular latency (shift) for a particular sector and recording channel. RESULTS: The variability of the corrected interocular latency decreased as the signal-to-noise ratio (SNR) of the mfVEP responses increased. For example, the 95% confidence intervals decreased from over 16 ms to under 4 ms as SNR increased. Grouping and summing the responses also lead to an increase in SNR and a decrease in the confidence interval. The results of various cluster criteria were also derived. A cluster criterion (e.g. two or more contiguous points within a hemisphere exceeding a given confidence interval), can serve to increase the specificity for detection of eyes or individuals with abnormal interocular latencies. For example, while 21% of the eyes had 3 or more points exceeding the 5% confidence interval, only 1.8% of the eyes had a cluster of 3 or more of these points. Finally, interocular latency was only weakly correlated with age (r = 0.26). CONCLUSION: In testing for abnormalities in interocular latencies, the confidence interval should be based upon the SNR of the response. Grouping and summing responses to increase SNR or employing a cluster test may also prove useful.

Acute Disease↗

PubMed2004

Determining abnormal latencies of multifocal visual evoked potentials: a monocular analysis.

PURPOSE: To describe a methodology for measuring abnormal timing of monocular multifocal visual evoked potentials (mfVEP). METHODS: The mfVEPs from 100 individuals with normal visual fields and normal fundus exams were analyzed. The stimulus was a 60 sector, pattern-reversing dartboard display. For each of the 60 locations of the dartboard and each channel and each eye, a template was derived based upon the average of the responses from the 100 normal individuals. In deriving this template, care was taken to exclude those responses reversed in polarity as compared to the average response. The best array of responses for each individual was compared to these templates. The relative latency of each response was measured as the temporal shift producing the best cross-correlation value. RESULTS: The 95% confidence interval (CI) decreased as the signal-to-noise ratio (SNR) of the mfVEP responses increased. For example, the 95% CI decreased from over 17 ms to under 9 ms as the SNR increased. Grouping and summing the responses also lead to an increase in SNR and a decrease in CI. Because the number of points exceeding the CI is not randomly distributed among normal individuals, a cluster criterion (e.g. two or more contiguous points within a hemisphere exceeding a given confidence interval) can be helpful. For example, while 18% of the eyes had 5 or more points exceeding the 5% confidence interval, only 6.5% of the eyes had a cluster of 5 of these points. The correlation between relative latency and age was relatively low (r = 0.46). CONCLUSION: For detecting abnormalities in the timing of monocular, mfVEP responses, a template method provides a reasonable approach. In devising a particular test for abnormal timing, the CI should be based upon the SNR of the response. In addition, grouping and summing responses to increase SNR or employing a cluster test may also prove useful.

Acute Disease↗