Border enhancement as a function of binocular fixation performance

Traditionally, fixation disparity is measured by interocular vertical alignment of unfusable monocular targets. The disparity generally increases with forced ocular vergences, producing characteristic individual functions. This study explores a new method of monitoring binocular fixation performance; the method is based on the effect of the distance of the border stimulus from the foveal center on the lateral spread of border enhancement. That is, as this distance increases, the enhancement spread increases. It is found that, as increasing ocular vergence is applied, the enhancement also increases, in a manner resembling conventional fixation disparity measurements. However, some dissimilarities between the border enhancement functions and the conventional functions suggest that the directional values used as a basis for the latter undergo modifications.