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.

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.

A substantial percentage of ON/MS patients show a long-term improvement in conduction velocity. Because this improvement can be local, the mfVEP should allow these improvements to be monitored in patients with ON/MS.

Aims: To determine the effect of glaucomatous damage on the latency of the multifocal visual evoked potential (mfVEP). Methods: Monocular mfVEPs were recorded from a glaucoma group (n = 50) defined by a glaucomatous disc and an abnormal visual field and a control group (n = 47). 25 patients were characterised as normal tension glaucoma (NTG) and 25 as high tension glaucoma (HTG). Monocular and interocular latency analyses of the more affected eye were obtained using custom software. Results: On interocular analysis, both the HTG and NTG groups showed a statistically significant increase in mean mfVEP latency with average relative latencies and percentage of points with significant delays of 1.7 ms and 10.3% (HTG) and 1.3 ms and 8.2% (NTG) compared to 20.3 ms and 2.7% (controls). On monocular analysis, only the HTG group showed a significant increase in latency with measures of 5.7 ms and 14.6% (HTG) compared to 3.2 ms and 10.6% (NTG) and 2.1 ms and 9.6% (controls). Using the 95th percentile of a normative group as the cut off, the sensitivity ranged from 20% to 38% and the specificity from 87% to 100% with the interocular analysis providing the best discrimination, Conclusion: Although up to 40% of patients showed delays in the mfVEP latency, these delays were modest, on average a few milliseconds. These results differ markedly from those of a recent conventional VEP study, which reported 100% sensitivity, 100% specificity, and an average delay that exceeded 25 ms. G laucoma, a widely prevalent eye disease, is characterised by an optic neuropathy, often associated with elevated intraocular pressure, leading to characteristic visual field defects and optic nerve head damage. It is well established that damage to the ganglion cells and/or their axons produce these visual field defects. What is less clear is the extent to which the ganglion cells undergo a rapid apoptotic death as opposed to lingering in an abnormal state. If the latter holds, then it raises the possibility of neuroprotection of unhealthy retinal ganglion cells. A possible indicator of the health of the retinal ganglion cells is the latency of their response.There have been a number of studies with conventional visual evoked potentials (cVEP) showing large latency delays, of the order of 20 ms, in glaucoma patients.1-5 A recent study 5 reported that all their patients with open angle glaucoma had abnormal cVEP latencies with an average latency that was 27.8 ms longer than the control group. Further, the cVEP latency has been used as a marker of reversible ganglion cell damage in trials of neuroprotective agents for the treatment of glaucoma. 6 The implication is that latency can be used as a measure of early glaucomatous damage before retinal ganglion cell death.A potential problem with the cVEP is that it represents the weighted sum of many local responses. Thus, the technique may obscure delays in local responses. These delays in latency should be seen more easily with the multifocal VEP (mfVEP). With the mfVEP technique, multiple responses, corr...