Editing Depth perception (section)

=== The law of Newton–Müller–Gudden ===
[[Isaac Newton]] proposed that the optic nerve of humans and other primates has a specific architecture on its way from the eye to the brain. Nearly half of the fibres from the human retina project to the brain hemisphere on the same side as the eye from which they originate. That architecture is labelled hemi-decussation or ipsilateral (same sided) visual projections (IVP). In most other animals, these nerve fibres cross to the opposite side of the brain.

[[Bernhard von Gudden]] showed that the OC contains both crossed and uncrossed retinal fibers, and Ramon y Cajal<ref name="Ramon Cajal 1972 pp 368-380">Ramon Y, Cajal S (1972): "Nerfs, chiasma et bandelenes optiques"; in ''Histologie du Système de l'Homme et des Vertébrés''. Madrid, Consejo Superior de Investigaciones Científicas, vol 2, pp. 368–380.</ref> observed that the grade of hemidecussation differs between species.<ref>Polyak S (1957): Investigation of the visual pathways and centers during Classical Antiquity, the Middle Ages, and the early period of the modern scientific Era; in Klüver H (ed): The Vertebrate Visual System. Chicago, University of Chicago Press, pp 113–115.</ref><ref name="Ramon Cajal 1972 pp 368-380"/> [[Gordon Lynn Walls]] formalized a commonly accepted notion into the law of Newton–Müller–Gudden (NGM) saying: that the degree of optic fibre decussation in the optic chiasm is contrariwise related to the degree of frontal orientation of the optical axes of the eyes.<ref>Walls, Gordon L. (1942): ''The Vertebrate Eye and Its Adaptive Radiation''. New York, Hafner.</ref>{{page needed|date=April 2020}} In other words, that the number of fibers that do not cross the midline is proportional to the size of the binocular visual field. However, an issue of the Newton–Müller–Gudden law is the considerable interspecific variation in IVP seen in non-mammalian species. That variation is unrelated to mode of life, taxonomic situation, and the overlap of visual fields.<ref>Ward R, Reperant J, Hergueta S, Miceli D, Lemire M (1995): "Ipsilateral visual projections in non-eutherian species: random variation in the central nervous system?" ''Brain Research Reviews'' 20:155–170.</ref>

Thus, the general hypothesis was for long that the arrangement of nerve fibres in the optic chiasm in primates and humans has developed primarily to create accurate depth perception, stereopsis, or explicitly that the eyes observe an object from somewhat dissimilar angles and that this difference in angle assists the brain to evaluate the distance.