Binocular vision. Binocular single vision (BSV); simultaneous use of two eyes to give a single image from bifoveal viewing. Binocular vision (BV); the simultaneous perception of two images from each eye. This may be in the form of diplopia or BSV. Investigation of binocular vision. To determine whether the aim of the treatment is to restore BSV or improve the patient’s appearance. A) Simultaneous pe rception/ retinal correspondence. Simultaneous perception of retinal images from either eye. May be corresponding (NRC) if both eyes have a common visual direction, giving single vision. Abnormally corresponding (ARC) when the fovea in one eye has a common visual direction with an extra foveal point in the other eye in a manifest strabismus, this facilitates a low grade of BSV. Suppression (pathological) occurs in constant and intermittent strabismus to over- come diplopia, confusion and incompatible images in high degrees of anisometropia. Bagolini glasses. Worths lights. B) Fusion. Sensory fusion the ability to appreciate two similar images from each eye and see them as one. Motor fusion the ability to maintain a single fused image during vergence movements. 20^BO prism. 1. inward movement of fixing eye. 2. conjugate movement of contralteral eye (herrings law) 3. diplopia stimulating convergence on contralateral eye. Prism fusion range. Horizontal vergence movements are induced to maintain binocular single vision using base in and base out and vertical prisms. C) Stereopsis. The perception of the relative depth from the two images, which stimulate disparate retinal points. Stereoacuity is an angular measurement of the minimum resolvable binocular disparity necessary for the appreciation of stereopsis.