Common pathological basis of the nervous ocular symptoms in chronic glaucoma.

CLINICALLY the main symptoms of chronic glaucoma (such as optic atrophy and ocular hypertension) appear to be independent, and the latter may be absent or may appear late. It is, therefore, desirable to be able to ascribe most of the symptoms of this disease to a common pathology. The pathogenesis of hypertension is difficult to establish, but that of optic atrophy and the field changes associated with a pathological tissue change is easier. This special form of atrophy of the nerve fibres, known as " lacunar or cavernous degeneration ", affects not only the preand retro-laminary portion of the optic nerve, but also spreads along the trunk into the brain. This cavernous atrophy is known to be independent of the increase of ocular tension, being due to a trophic disturbance in the fibre. Duke-Elder (1940) thinks it to be an ischaemia due to a sclerosis of the nutritional vessels, and Wolff (1947) thinks it results from a reduction of blood flow. As the nerve fibre is the most differentiated, it is the first to be modified and to disappear. The histo-pathological findings are not always in agreement, and it is not possible to say whether characteristic vascular alterations are present in glaucomatous atrophy. According to Elschnig (1928), the reduction of the number of capillaries distinguishes the glaucomatous from other forms of nervous atrophy. The meshes appear interrupted and the individual lumina are often obliterated. Loewenstein (1945) tried to correlate the findings of nervous atrophy in glaucoma with the histo-pathological vascular findings, and frequently found a thrombotic occlusion of the smallest vessels. The purpose of this research, therefore, was to investigate the nature of the vascular alteration of the nerve fibre in glaucoma.