Increased latency of visual evoked potentials in healthy women during menstruation.

Dear Editor,

We congratulate Dr. Azarmina and colleagues on their study investigating the latency of visual evoked potentials (VEPs) among healthy females during and after menstruation.1 The authors found significantly increased latencies in pattern and flash VEP in their subjects. Their findings are particularly remarkable since the mean latency of the P100 wave was increased by approximately 20 ms (mean increase of 18.7%) causing VEP traces to become almost unreliable for evaluating visual pathway diseases. There are few other studies describing delayed VEP latencies over the luteal phase, yet the changes have not been as much.2,3

The authors presented only one pattern VEP (PVEP) waveform while these traces are as valuable as amplitude and latency figures. Therefore, we kindly ask Dr. Azarmina and colleagues to present at least 5 more PVEP traces to further illustrate waveform changes during the menstrual cycle. Careful analysis of these alterations reveals whether or not the follicular phase has an amplitude enhancing/ latency decreasing/waveform changing effect.

AUTHORS’ REPLY

Dear Editor,

We would like to thank Dr. Gundogan and colleagues for their interest in our paper titled “Increased Latency of Visual Evoked Potentials in Healthy Women during Menstruation” previously published in JOVR.

As information on latency changes during and after menstruation was already presented in a table in our article, only a single PVEP tracing was depicted. However, at this request, we provide more waveforms obtained after menstruation (during elevated estrogen levels) and on the maximum bleeding day (high progesterone levels) (Figure 1, A and B respectively).

Different factors that may interfere with the transmission speed of electrical waves within the optic nerve influencing PVEP latency values have been discussed in our article.

Decreased VEP amplitude is generally observed in conditions where axons of the optic nerve are destroyed, e.g. ischemic optic neuropathy and optic atrophy. In inflammatory lesions such as multiple sclerosis and other disorders involving the myelin layer, the time- related parameter (latency) is more likely to be disturbed.