Pathway of Centrifugal Fibres in the Human Optic Nerve, Chiasm, and Tract.

THE pathway of the centrifugal (efferent, antidromic) nerves has been studied histologically in the optic nerves, chiasm, and optic tracts of a patient who had both eyes enucleated 50 years before. Centrifugal fibres in the optic nerve of animals have been known to exist for a long time (Cajal, 1894; Dogiel, 1895), and this fact is supported by recent physiological observations (Granit, 1955; Dodt, 1956). There can no longer be much doubt that a great number of centrifugal nerves also exists in the human optic nerve. Numerous remaining nerve fibres in two atrophic nerve stumps eleven and sixteen years after enucleation were the first evidence (Wolter and Liss, 1956). Subsequently, the terminal branches of centrifugal nerves were demonstrated in the normal human retina and optic nerve (Liss and Wolter, 1956; Wolter, 1957a) and it was concluded that at least some of the centrifugal nerves supply blood vessels. The observation of interrupted neurites in the human nerve fibre layer with terminal swellings pointing away from the optic disc was further evidence of the presence of centrifugal fibres (Wolter, 1956). Attempts at regeneration of centrifugal fibres were observed in a child's optic nerve stump eleven days after enucleation (Wolter, 1960) and later the reactions of these fibres could be studied four days after enucleation (Pfister and Wolter, 1963) in another case. A peculiar proliferation (hyper-regeneration) of centrifugal nerves was observed around blood vessels and micro-aneurysms in advanced diabetic retinopathy (Woltei, 1961). Very recently the remaining centrifugal nerves in the human optic disc were examined histologically ten days after complete occlusion of the central retinal artery that caused necrosis of the ganglion cells and all centripetal (afferent) retinal nerves (Wolter, n.d.). This latter study allowed for the conclusions that there are several morphologically different types of centrifugal nerves and that about 10 per cent. of the nerves in the normal human optic disc are centrifugal in nature.