Binocular Single Vision; Fusion.—In all but a small minority of cases binocular fixation is present whenever one looks with both eyes. The image of the object looked at, then, is formed on each fovea (fig. 1).
Yet, though there are two images, one sees, not two objects, but one object (binocular single vision). For the mind by a peculiar process which we denominate fusion combines the two retinal images into a single visual impression, which differs notably from the impression derived from each eye when seeing separately.
Fusion of Images Formed on Corresponding Points.—Not only does the mind fuse the two retinal images of any object looked at directly, but it also fuses the images of a number of objects seen by indirect vision. Fusion, in fact, occurs for any object, the retinal images of which fall on corresponding points, i. e., on the two points
DUANE A. BINOCULAR VISION AND PROJECTION. Arch Ophthalmol. 1931;5(5):734–753. doi:10.1001/archopht.1931.00820050056005
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