Binasal occlusion is a method of partial covering (occlusion) of the visual field of the two eyes in which the sector of the visual field that is adjacent to the nose (the nasal visual field) is occluded for each eye. It is a well-known procedure in

vision therapy Vision therapy (VT), or behavioral optometry, is an umbrella term for alternative medicine treatments using eye exercises, based around the pseudoscientific claim that vision problems are the true underlying cause of learning disabilities, parti ...

. By blocking parts of the image that would be seen by both eyes, binocular occlusion reduces the visual stress that would be related

diplopia Diplopia is the simultaneous perception of two images of a single object that may be displaced horizontally or vertically in relation to each other. Also called double vision, it is a loss of visual focus under regular conditions, and is often v ...

and

binocular rivalry Binocular rivalry is a phenomenon of visual perception in which perception alternates between different images presented to each eye. When one image is presented to one eye and a very different image is presented to the other (also known as dic ...

. In contrast to an

eye patch An eyepatch is a small patch that is worn in front of one eye. It may be a cloth patch attached around the head by an elastic band or by a string, an adhesive bandage, or a plastic device which is clipped to a pair of glasses. It is often worn ...

that occludes the whole visual field of one eye, binocular occlusion allows some degree of binocular vision; more particularly, it emphasizes the role of binocular functioning in

peripheral vision Peripheral vision, or ''indirect vision'', is vision as it occurs outside the point of fixation, i.e. away from the center of gaze or, when viewed at large angles, in (or out of) the "corner of one's eye". The vast majority of the area in th ...

: objects that are located to the right can only be fixated by the right eye, and those located to the left only by the left eye. This in particular prevents the cross-fixation. Cross-fixation which occurs in some

strabismus Strabismus is a vision disorder in which the eyes do not properly align with each other when looking at an object. The eye that is focused on an object can alternate. The condition may be present occasionally or constantly. If present during a ...

patients with

esotropia Esotropia is a form of strabismus in which one or both eyes turns inward. The condition can be constantly present, or occur intermittently, and can give the affected individual a "cross-eyed" appearance. It is the opposite of exotropia and usual ...

, and is, in particular, characteristic for a form of infantile esotropia also known as Cianci's syndrome. Binasal occlusion is used in treatment of patients with sensory deficits due to complications of traumatic brain injury or having had a stroke, as well as patients with

, esotropia, convergence excess, divergence insufficiency, or visual overstimulation. According to a 2017 paper, another hypothesis of the effectiveness of binasal occlusion in the treatment of Post Trauma Vision Syndrome, is the tape provides a stationary reference point that the brain can use to help decode the incoming visual information. The term Visual Motion Sensitivity is coined in this paper.

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