Visual sensitivity across the menstrual cycle

This study was designed to evaluate the hypothesis that hormonal change can affect lower level light-adaptation processes, which are likely to be retinally based. Foveal visual sensitivities were measured across several menstrual cycles of four women not using hormonally acting medication and across several menstrual cycles of three women using a triphasic oral contraceptive. One woman, diagnosed with premenstrual syndrome (PMS), was a subject for both groups. Sensitivities were measured for a series of test wavelengths for 580-nm backgrounds of 2.0 and 4.0 log td. Of the six individuals tested, one had clear evidence of visual-adaptation changes occurring in phase with the menstrual cycle. Prior to using the oral contraceptive, this individual (the PMS subject) experienced changes of short-wavelength-sensitive (SWS)-cone-mediated sensitivities of up to about 1.4 log unit on the 4.0 log td background. Her SWS-cone-mediated sensitivities tended to be highest near ovulation and lowest premenstrually. Threshold-versus-illuminance (TVI) curves confirmed that the rate of sensitivity decrease with increasing background illuminance (i.e. the TVI slope) was greater premenstrually. The degree of background-induced desensitization within her middle-wavelength-sensitive (MWS)/long-wavelength-sensitive (LWS) cone pathways also appeared to vary cyclically, but the magnitude of the variation was smaller and the time course appeared to be different. When this subject began oral contraceptive use, the patterns of sensitivity change were all altered. None of the other five subjects experienced changes of SWS-cone-mediated vision that were cyclic and significantly adaptation-state dependent. However, there was evidence for a limited degree of cyclic adaptation change within the MWS/LWS cone pathways of at least one additional subject. We conclude that hormonal change can--for some unknown proportion of women--be linked to alterations of retinal function. However, the alterations are not the same for all visual pathways, and there are pronounced individual differences. The data also demonstrate that individuals' visual adaptation capabilities can vary substantially over periods of weeks.