Experimental allergic optic neuritis in guinea pigs: preliminary report.

An experimental model for acute allergic optic neuritis was produced in adult strain 13 guinea pigs by sensitization with isogenic spinal cord emulsion in complete Freund's adjuvant. These animals exhibited two distinct clinical patterns: (1) "retrobulbar optic neuritis," with a diminished pupillary response to light despite a normal fundus, and (2) "neuroretinitis," with a diminished pupillary response associated with hyperemia and swelling to the disc and juxtapapillary retinal edema. Histopathologic study of those animals with "retrobulbar neuritis" revealed that some had no abnormalities in the optic nerve or chiasm, but showed foci of mononuclear cell infiltration in the brain. Others had a mononuclear cell infiltration localized to the retrobulbar portion of the optic nerve and chiasm with multiple foci of axial and periaxial demyelination. Similar pathologic changes were present in the animals with "neuroretintis", but the lesions were located just behind the lamina scleralis. These animals also exhibited marked swelling of the axons at the lamina retinalis. On examination by light microscopy, the alterations in the region of optic nerve head appeared characteristic of papilledema.