Retrograde degeneration of primary optic fibers in the cat

Unilateral electrolytic lesions were placed in the optic tract of adult cats, midway between the optic chiasm and the ventral lateral geniculate nucleus, or in the terminal portions of the tract. Transection of one optic nerve was performed in other cases. The animals were maintained postoperatively for 2–21 days. A few cats with long-standing optic-nerve incision were also available. The brain and nerve sections were processed with three current silver methods for the study of axonal disintegration in the primary optic pathways distal (retinal) to the lesions. In all cases retrogression could be seen in those parts of the optic tract or nerve near the lesions (traumatic degeneration). The amount and extent of decomposition distally from the lesion site was related to the length of the postoperative survival and to the proximity of the lesion to the retina. These findings favor an interpretation involving retrograde deterioration of afferent (centripetal or retinofugal) optic fibers, and fail to confirm the often suggested existence of efferent (centrifugal or retinopetal) fibers in the cat.