Riddoch syndrome (also known as the Riddoch phenomenon) is an ocular affectation often caused by lesions in the occipital lobe which limit the sufferer's ability to distinguish objects. Only moving objects in a blind field are visible, static ones being invisible to the patient. The moving objects are not perceived to have color or detail. The subject may only have awareness of the movement without visual perception of it (gnosanopsia), or the general shape of a moving object may be perceivable as a shadow like outline.
At least one patient was able to use a rocking chair—putting non-moving surroundings in relative motion to her head—to improve her motion perception. She eventually was able to do the same with just voluntary movement of her head.