The effects of target orientation on the dynamic contrast sensitivity function

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Virginia Tech

Much research has been accomplished on the effects of target motion on visual acuity. Research has also been accomplished on the effects of target orientation on visual acuity. The contrast sensitivity function (CSF) also has been studied as a predictor of visual performance under dynamic conditions. However, no previous studies have combined these areas of research and examined the effect of target orientation on the Dynamic Contrast Sensitivity Function (DCSF).

This study examined the effects of target orientation on the DCSF and found that diagonal lines (relative to vertical lines) decreased the DCSF, on average over 19%. Previous research indicated that target motion reduces contrast sensitivity, and at the same time shifts the peak of the CSF toward lower spatial frequencies. This study rotated the target in a circular path (velocities of 22°, 30°, and 39°/second) and found a similar decrement and shift in the CSF.

The main effects for Target Orientation, Velocity, and Spatial Frequency and their two-way interactions were all statistically significant (p ≤ .05). Additionally, all velocity conditions were found to be statistically different from each other. These results advance the validity of our measurement device and procedures.

The effect of target orientation presumably is a function of the magnocellular and parvocellular visual pathway systems and their roles in the detection of form and motion. While the magnocellular system is primarily responsible for detection of motion and large objects, the parvocellular system is responsible for the detection of color and fine detail.