OVULATION ENHANCES THE PHOTOPIC ERG IN WOMEN

Abstract

Abstract: : Purpose: Animal experiments suggest that estrogen can enhance (acute effect) or suppress (chronic effect) the ERG. Can this be demonstrated in normally cycling women? Methods: Photopic (flashes:–0.80 to 2.84 log cd.s.m^–2; background 30 cd. m^–2) and scotopic (flashes: –3.21 to 0.39 log cd.s.m^–2; 30 minutes of dark–adaptation) ERGs were obtained from normally cycling (not on oral contraceptives) women (N=5; 18–22 years old). Time of ovulation was determined with the Clear Plan® fertility monitor. Subjects were tested 4 times, on two consecutive cycles, as follows: follicular phase (5–7 days after onset of menses), ovulation (2 consecutive days as per Clear Plan® readings) and luteal phase (2–8 days prior to onset of the next cycle). Data was compared to that obtained from age–matched male subjects (2 recording sessions 1 week apart). Results: As previously reported, female ERGs are significantly larger than males’(average: 25% larger). Male ERGs did not demonstrate significant intersession variability. In contrast, the photopic responses (V_max but not retinal sensitivity k) of women obtained on the two sessions closest to ovulation were always equally larger (10–15%) than follicular and luteal measurements which were not significantly different from each other. Interestingly, the scotopic responses (V_max and retinal sensitivity k) did not demonstrate a similar trend. Conclusions: The small (but reproducible from cycle to cycle) enhancement of the photopic ERG at ovulation (where plasmatic estrogen peaks) is compatible with our animal results. While the photopic (cone) specificity of this effect remains to be elucidated, it could have a significant impact in responses soliciting more specifically (than full–field conditions) smaller population of cones (i.e. S–cone ERGs or multifocal ERGs) or in the diagnosis or follow–up of cone disorders. Consequently as a precautionary measure, clinical ERG data files should include the date of last menstruation. Supported by CIHR and FRSQ Réseau–Vision.

Keywords: electroretinography: non–clinical • clinical laboratory testing • retina