Evidence for separable binocular processes differentially affected by artificially induced anisometropia

Two measurable effects are produced by viewing a large disk rotating about the line of sight: a perceived displacement of the apparent horizon (tilt) and cyclotorsion of the eye (torsion). Previous results in our laboratory (see Refs.) using dichoptic presentation techniques show that both effects demonstrate binocular enhancement in normal subjects. Further, stereoblind subjects maintain enhancement for the oculomotor effect, torsion, but not for the perceptual effect, tilt. In this study we have found that this stereoblind pattern of results can be produced optically in normals by introducing a three diopter myopia in one eye. This renders the subject stereoblind and causes suppression of the artificially myopic eye. In this condition torsion still shows enhancement; tilt does not. This procedure may be useful in isolating causes of stereoblindness and in locating different sites of binocular interaction.