Current binocular stereoscopic displays cause visual discomfort when objects with large disparities are present in the scene. One solution for improving visual comfort is synthetic depth-of-field processing, which simulates the characteristics of a human visual system. With this technique, visual comfort is improved by blurring portions of the background and/or foreground in the scene. However, this technique has the drawback of degrading overall image quality because the blurring is typically applied to both left and right images. To alleviate the visual discomfort, we propose a novel disparity-based asymmetrical filtering technique. Proposed technique applies the filtering to the image of one eye only, and controls the blur level according to the disparity information between stereoscopic images. We investigate the effects of this technique on stereoscopic video by measuring visual comfort and apparent sharpness. Our results indicate that disparity-based asymmetrical filtering can improve visual comfort of stereoscopic video while it maintains apparent sharpness if unfixated regions with large disparities are blurred under the appropriate filtering condition