The optic nerves and bony canals from 36 male Holstein calves (23 vitamin A-deficient and 13 adequate) and four 2-year-old heifers (two deficient and two adequate) from five vitamin A experiments were examined. Severe constriction of the optic nerve, which resulted in demyelinization and malacia, was encountered in 14 of the deficient calves, whereas no changes were seen in the older deficient heifers. It is concluded that in the vitamin A deficient growing calf with markedly increased cerebrospinal fluid pressure, altered bone growth, and thickening of the dura mater occur. This is accompanied or followed by vascular occlusion and ischemic necrosis of the nerve as it passes through the optic canal.
Hayes KC, Nielsen SW, Eaton HD. Pathogenesis of the Optic Nerve Lesion in Vitamin A-Deficient Calves. Arch Ophthalmol. 1968;80(6):777-787. doi:10.1001/archopht.1968.00980050779019