TY - JOUR
T1 - Determining abnormal interocular latencies of multifocal visual evoked potentials
AU - Hood, Donald C.
AU - Zhang, Xian
AU - Rodarte, Christopher
AU - Yang, Bo E.
AU - Ohri, Nitin
AU - Fortune, Brad
AU - Johnson, Chris A.
PY - 2004/9
Y1 - 2004/9
N2 - 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.
AB - 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.
KW - Electrophysiology
KW - Latency
KW - Multifocal visual evoked potential
KW - VEP
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U2 - 10.1007/s10633-004-5511-1
DO - 10.1007/s10633-004-5511-1
M3 - Article
C2 - 15881264
AN - SCOPUS:16344390269
SN - 0012-4486
VL - 109
SP - 177
EP - 187
JO - Documenta Ophthalmologica
JF - Documenta Ophthalmologica
IS - 2
ER -