Prismatically induced eye strain and autokinetic direction frequency.

Autokinetic movement (AKM) as assessed by number of reported direction changes was evaluated for 25 college sophomores as a function of prism displacement strength. The results indicated that the strain on the eye muscles produced by prism displacement significantly affected frequency of direction change reports: the greater the displacement, the fewer the number of reported direction changes. These results were interpreted according to outflow theory in terms of the prism-imposed strain effectively increasing the level of noise in the outflow monitoring system, thereby making the detection of a cancelling response signal, the direction change, more difficult.