Role of the ciliary circulation

Clinically the presence of nerve fibre bundle defects in glaucoma and non-glaucomatous lesions, and altitudinal or vertical hemianopias in pre-chiasmal lesions has been known for a long time. These suggest a sectoral lesion in the optic nerve or retina. In the majority of such cases, no retinal lesion is seen to account for these visual field defects. It has been presumed that the lesion lies in the optic nerve. Such a visual field defect can be produced only by a sectoral lesion. Most of these field defects are considered to be vascular in origin, but studies of the blood supply of the optic nerve have so far failed to demonstrate any segmental blood supply to the nerve which could explain them. The present study demonstrates such a sectoral blood supply in the optic nerve head and choroid and is of considerable significance in explaining the site of the lesion and the pathogenesis of these defects.