Changes in visual evoked potentials during the menstrual cycle in young women

Abstract

Background: The visual evoked potential (VEP) is a form of an electrical signal. VEP originates from the visual cortex which is located in Brodman areas 17 and 18 of the occipital lobe. VEP is generated in response to stimulation of the retina by light flashes or pattern stimuli. The advent of VEPs in the 1970s first allowed clinicians to assess neural conduction in the optic nerve. There are many factors that affect VEP such as age and gender; one among them is the hormonal factor. Ovarian and thyroid hormones are vital factors in the generation of olfactory, taste, visual, and auditory neuronal activity. The ovarian hormones progesterone and estrogen play a major role in the conduction of the optic nerve. Aims and Objectives: The aims and objectives of the study are to evaluate the influence of ovarian hormones in the VEPs. Materials and Methods: Among the 1st year medical students, 26 young females (18–20 years of age) were randomly selected. Informed consent was obtained from them and the institutional ethical committee approved the study. Students having regular menstrual periods for the past 6 months with normal visual acuity were included. Those with a history of polycystic ovarian disease, having irregular periods, under hormonal treatment were excluded from the study. Detailed history helps in identifying the proliferative and secretory phases of the menstrual cycle. The P100 wave latency of VEPs was recorded during these two different phases. Results: An unpaired t-test was used for analyzing the data. While comparing the proliferative and secretory phases, P100 wave latency was significantly reduced in the proliferative phase (101±3.6 vs. 97.9 ± 1.43 ms; P < 0.0001). Conclusion: The receptor sensitivity in the visual pathways to dopamine is increased by estrogen which in turn leads to a decrease in the time taken by the visual impulses to reach the visual cortex. Progesterone antagonizes estrogen activity in the central nervous system. Therefore, estrogen is responsible for the reduction in latency during the proliferative phase and progesterone is responsible for the prolonged VEP latency in the secretory phase. Thus, the excitability of the visual system is influenced by the ovarian hormones.