Visual Sensitivity Across the Menstrual Cycle

Abstract

Abstract: : Purpose: This research follows 1) from reports that age-related changes of SWS-cone mediated vision are gender-dependent, 2) from reports that the retina contains estrogen receptors, and 3) from ongoing research that selective estrogen receptor modulators used against breast cancer affect visual adaptation within SWS-cone pathways. This research aims to determine whether cyclic hormonal changes affect visual adaptation within SWS-cone pathways of young healthy women. Methods: Foveal increment thresholds were measured 5 days/week across several menstrual cycles. A series of test wavelengths (440-nm to 640-nm) were presented on each of two 580-nm backgrounds: dim (2.0 log td) and bright (4.0 log td). Test stimuli were 3ºdiameter discs. Three subjects were tested. One subject (S1) had normal menstrual cycles and was not using any hormonal contraception methods. She subsequently began using a triphasic progestin oral contraceptive. Two other subjects (S1 & S2) used the same triphasic contraceptive. For S1 only, TVI curves were measured at several stages during the natural menstrual cycle. Results: While S1 was not using any hormonal contraceptive, sensitivities varied cyclically across the menstrual cycle. SWS-cone-mediated sensitivities assessed with short-wavelength tests (< 490-nm) on the bright background were highest at ovulation and lowest premenstually, several days prior to menses. The peak-to-trough sensitivity difference was about 1.6 log units. For all other test/background combinations, the highest sensitivities occurred near the end of menses. The peak-to-trough difference was about 0.5 log units on the dim background, but closer to a log unit on the bright background. The difference of log sensitivities for short wavelength tests on the bright vs dim background varied across the menstrual cycle in a quantitatively similar way (r=.93) to the difference of log sensitivities for short vs longer (≷ 540-nm) wavelength tests on the bright background. TVI curves for SWS-cone-mediated response were about 1.8 times steeper premenstrually than at ovulation. At the longer test wavelengths, the TVI slopes did not vary. When S1 began using the oral contraceptive, the magnitude of SWS-cone-mediated sensitivity variations still approached 1.6 log units, but the timing changed dramatically. The sensitivities of S2 varied cyclically and concurrently for all conditions, but only by about 0.3 log unit from peak-to-trough. The sensitivities of S3 did not vary cyclically. Conclusion: Female hormones can affect visual adaptation within SWS-cone pathways and can alter overall sensitivity levels. There may be substantial hormonal response differences between individuals.

Keywords: 384 dark/light adaptation • 362 color vision