Perimetry of contrast detection thresholds of moving spatial sine patterns. II. The far peripheral visual field...

Contrast detection thresholds for moving sine wave gratings were obtained at the fovea and at eccentricities of 6 degrees, 12 degrees, 21 degrees, 32 degrees, and 50 degrees on the nasal horizontal meridian. The field subtended 4 degrees X 4 degrees. Spatial frequencies ranged from 0.25 cpd up to the resolution limit, temporal frequencies from 0.1 Hz up to the CFF. Mean retinal illuminance was 10 trolands. We find for these conditions: (i) For any eccentricity there exists a unique combination of spatial frequency and velocity for which the threshold is a minimum. (Extremes are 2 cpd and 2 degrees s-1 at the fovea, and 0.5 cpd and 12 degrees s-1 at an eccentricity of 50 degrees. (ii) Acuity depends little on velocity, the CFF only little on spatial frequency. (iii) The higher the eccentricity, the higher the threshold for any drifting sine wave pattern. Except for this the qualitative threshold behavior as a function of spatial and temporal frequency is identical at the fovea and at eccentricities up to 50 degrees. The thresholds double every 12 degrees for spatial frequencies of 0.25-2 cpd. For a given spatial frequency the visual field is blind beyond a certain critical eccentricity. This critical eccentricity is a monotonically decreasing function of spatial frequency.