Capillary-glia relationships in the human optic nerve, chiasma, and tract, as shown by phase-colour contrast and microdissection.

IN the optic nerve, chiasma, and tract the component most closely associated with the blood vessels is the neuroglia. It has become increasingly appreciated that in the brain and spinal cord the neuroglia has a dynamic role to play in metabolic processes, and is no longer to be regarded as primarily a supporting matrix; on the details of its association with the vascular system there is little agreement. As an extension of the central nervous system, the complex glial system in the optic nerve, chiasma, and tract can be expected to play an equally important part in function and pathology. In view of the importance of the relationship between the vascular system, especially the capillaries, and the neuroglia and the metabolic activity of the neural elements in the central nervous system, an investigation was carried out by new methods to determine the distribution and relationships of the perivascular glia in normal human optic nerve, chiasma, and tract. The normal capillary-glia architecture in different regions of the optic system must be taken into account in instances of visual field defects which arise as the result of vascular disturbance or some other pathological condition. It is perhaps in the capillary-glia architecture that we might seek an explanation of certain differences in visual field defects which result from disturbances in the vascular system. The literature on the glia of the optic system is remarkably scarce. Liss (1956) remarked that he could find only three reports on the astroglia in the optic nerve (Marchesani, 1926; Cone and Macmillan, 1932; Kolmer, cited by Lauber, 1936). The astroglia are the elements of the neuroglia which have special relationships to the vascular system. Cone and Macmillan (1932) cited Marchesani's description of the astroglia in the optic nerve as shown by staining methods, and mentioned that the glia intervened in a typical manner between the vascular and nervous systems at the lamina scleralis. This followed the view of Achucarro (1918), who regarded this relationship as characteristic of the whole central nervous system. Cone and Macmillan (1932) stated that the neuroglial cells in the optic system did not differ in any way from those in the brain and spinal cord.