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Sarah Elliott, David Peterzell; Individual differences in contrast sensitivity functions with and without adaptive optics: direct estimates of optical and neural processes in young and elderly adults using factor analysis. Journal of Vision 2017;17(10):791. doi: 10.1167/17.10.791.
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© ARVO (1962-2015); The Authors (2016-present)
Elliott et al. (2009) measured contrast sensitivity functions (CSFs) in young and elderly adults, using both normal viewing and closed-loop adaptive optics (AO) to correct high-order aberrations. To better characterize optical and neural processes, we reanalyzed these data using factor analytic techniques developed to estimate the number and tuning of spatial mechanisms (Peterzell, 1991; 2016). Log CSFs for 16 individuals, spanning two age groups (18-29, and 76-82 years), were measured using 2AFC for six horizontal, monocular sinewave gratings between spatial frequencies of 0.55 and 18 cpd . An oblique solution (direct oblimin) revealed three factors. The first loaded onto all AO data at and above 1.25 cpd, and also onto 1.25 cpd in the non-AO condition. This high frequency factor represents variability in neural or retinal contrast sensitivity consistent with parvocellular processing. The second factor loaded onto low frequencies (0.55 to 2.25 cpd, for both AO and normal viewing). It represents neural contrast sensitivity below 2.25 cpd, but also accounted for uncorrected contrast sensitivity at low frequencies (i.e., optical aberrations did not influence sensitivity at low frequencies). This is consistent with magnocellular processing. The third factor loaded onto 4.5 cpd and higher, but only for the normal, non-AO condition. This factor clearly represents optical quality as it was eliminated under AO correction. In sum, two neural factors were revealed when the optical factor was removed, either due to the specific frequency being tested (e.g., low frequencies are nearly un-affected by optical factors) or due to AO correction, and one optical factor was revealed at high frequencies with no AO correction. However even with optical aberrations removed temporarily, individual differences in the neural factors correlated with individual differences in uncorrected optics. Older individuals tended to have a poorer optical quality, but also showed less contrast sensitivity in both neural factors.
Meeting abstract presented at VSS 2017
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