Estimation of spatial scale across the visual field using sinusoidal stimuli

To characterize contrast sensitivity for sinusoidal stimuli across the central visual field and help bridge the gap between perimetry and visual psychophysics by developing a contrast-sensitivity template for spatial scale (experiment 1) and testing it on a new dataset (experiment 2).

In experiment 1, 40 subjects free of eye disease, ages 43 to 84 years, had one eye tested. Twenty-three locations along the horizontal and vertical meridians were tested with sinusoidal stimuli having peak spatial frequencies of 0.5, 1.0, and 2.0 cpd and a spatial bandwidth of 1.0 octave. Contrast sensitivity functions were fit with a low-pass template slid horizontally on a log-log plot by a spatial scale factor. In experiment 2, 29 of the original subjects had one eye tested. Twenty-six locations in grid form were tested with sinusoidal stimuli having peak spatial frequencies of 0.375, 0.53, 0.75, and 1.5 cpd. Spatial scale values were predicted using the 0.375 cpd data and template and compared to empirical values determined from the remaining data.

In experiment 1, the change in spatial scale alone fit the mean sensitivities well (residual sum of squares = 0.01 log unit). Spatial scale increased with eccentricity except for horizontal nasal displacements between 3° and 15°. In experiment 2, differences between empirical and predicted spatial scale values were within ±0.1 log unit (mean and SEM: 0.00 ± 0.01 log unit).

Spatial scale characterized the visual field tested in perimetry well and can contribute to further linkage between clinical perimetry and basic vision science.