TY - JOUR
T1 - Determining abnormal latencies of multifocal visual evoked potentials
T2 - A monocular analysis
AU - Hood, Donald C.
AU - Ohri, Nitin
AU - Yang, Bo E.
AU - Rodarte, Christopher
AU - Zhang, Xian
AU - Fortune, Brad
AU - Johnson, Chris A.
PY - 2004/9
Y1 - 2004/9
N2 - 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.
AB - 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.
KW - Electrophysiology
KW - Latency
KW - Multifocal visual evoked potential
KW - VEP
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U2 - 10.1007/s10633-004-5512-0
DO - 10.1007/s10633-004-5512-0
M3 - Article
C2 - 15881265
AN - SCOPUS:16344396310
SN - 0012-4486
VL - 109
SP - 189
EP - 199
JO - Documenta Ophthalmologica
JF - Documenta Ophthalmologica
IS - 2
ER -