The effect of simulated scotomas on visual search in normal subjects.

A simulated scotoma was stabilized on the fovea of 23 normal human subjects while they searched for acuity targets in arrays of non-targets. Search time doubled with a 20 min arc scotoma, and eye fixation duration increased by about 15% when compared to no-scotoma control conditions. Search difficulty was graded by adjusting acuity target size, search element density and contrast. Search time and eye fixation duration generally increased with display difficulty in no-scotoma conditions. Results are discussed in terms of sensory loss and motor disruption due to the simulated scotoma. The simulated scotoma method may be useful in studying adaptation to visual field loss in patient populations where the size, position and severity of the scotoma can be controlled.