Diffusion (Franz. fusion - fusion) is a complex physiological mechanism of view, providing for the merger of two monocular of pictures in a single visual image. In the mechanism of fusion distinguish two components: motor (opto-motor fusion reflex) and touch (actually a fusion). Understanding of the mechanism of fusion gives experience with prisms. If binocular fixation of the object to be attached to one of the lens of the eye, the image of the subject in the eye moves from the Central area of the retina, i.e. will be located in relation to the other eye is not at the offset, and disparate area of the retina. Double vision appears. To get rid of him, eyes makes a fusion movement, and the image in the eye again moves to the Central area of the retina. Once that happens, in effect sensor fusion - psychophysiological the act of unification of the two monocular images into a single whole.
Fusion movement may take place only in the known boundaries that define how the amplitude, width of fusion, or fusional reserves. The amplitude of fusion is defined by the maximum amount of convergence and divergence, as well as supra - and inframarginal, which is still possible binocular merging. Fusional reserves in the direction of convergence and divergence are called respectively positive and negative; vertical reserves the right and left superfusion reserves depending on what the eye rejected upwards. In norm positive width of fusion (for distance and near vision) is 24-28 prism diopters (D); negative width of fusion for Dali 7-8Δ and near 16-18Δ; vertical width of fusion - 3-4Δ.
Sufficient strength and width of fusion ensure the sustainability of binocular vision (see). Restoration of normal amplitude of fusion is one of the important tasks orthoptic treatment of strabismus (see) and heterophoria (see).