Band atrophy of the optic nerve. The histology of temporal hemianopsia.

Cross sections of the orbital portion of the optic nerve, the decussating fibers of which underwent atrophy, have a distinctive histologic pattern. Distally, from the eyeball to the midportion of the optic nerve, this pattern of atrophy consists of a broad-based nasal and a narrow-based temporal sector that form a horizontal band. Proximally, near the optic canal, the pattern changes. The atrophic bundles occupy the nasal and central portions of the optic nerve only.