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A. Eisner, S. Demirel; Does Phytoestrogen Consumption Affect Vision?. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5335.
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Previous studies (Eisner & Toomey, Vision Res. 2008) have indicated that reduced estrogen activity can affect vision mediated via short-wavelength-sensitive (SWS) cones. Independently, there is much public-health debate as to whether consuming phytoestrogen-rich foods - mainly soy and flax products - may militate against age-related cognitive decline due to reduced estrogen synthesis. By assessing SWS-cone-mediated vision, an isolatable central nervous system (CNS) pathway can be examined non-invasively and quantitatively, and might ultimately be used to mark other CNS changes that result from estrogen reduction but that may be delayed by phytoestrogen consumption.
Subjects were 44 healthy amenorrheic women (48-69 years). Age-corrected visual field sensitivities were obtained using Short Wavelength Automated Perimetry (SWAP) and conventional white-on-white (W/W) perimetry, in each case using standard 200 msec stimuli. SWS-cone-mediated sensitivities were measured at the fovea in Maxwellian View (1.5 Hz square-wave modulation). Half the subjects reported consuming soy and/or flax products, and half reported not consuming these products. For 15 subjects, the foveal critical flicker frequency (CFF) was measured for SWS-cone-mediated response at 0.5 log units above threshold, to assess temporal resolution.
Overall, the degree to which SWAP sensitivity decreased with retinal eccentricity was significantly less for soy/flax consumers than non-consumers, even when compared to the W/W data. However, this effect depended significantly on age, with the between-group differences being greatest for the youngest subjects. At the fovea, the SWS-cone-mediated sensitivities of the soy/flax consumers were significantly lower that those of the non-consumers after age adjustment in an Analysis of Covariance, possibly because the significantly poorer temporal resolution of the soy/flax non-consumers corresponded to longer temporal integration periods. This suggestion is supported by the observation that the CFF values and foveal sensitivity levels correlated inversely (r = -.54, p = .036).
The results suggest that consumption of soy and/or flax products may delay the onset of age-related functional loss (response slowing) within a CNS pathway that is readily assessable. Future studies directly measuring phytoestrogen exposures are warranted.
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