Vitamin A, beta carotene, and hereditary buphthalmus in the rabbit.

Rabbits with hereditary buphthalmus, AXBU/J strain, were fed various levels of supplementary vitamin A or its precursor beta carotene, in addition to a vitamin A deficient diet, to test the hypothesis that the bu gene acts by reducing either the conversion of beta carotene to vitamin A or the utilization of vitamin A. Measurements were taken on an age series of skulls of manifest and of prodromal buphthalmics to see if there were any observable differences in optic foramen size associated with the clinical manifestations of buphthalmus. Constriction of the optic nerve by bone alteration has been reported to be associated with vitamin A deficiency. The original hypothesis was not a tenable one as the rabbit with hereditary buphthalmus readily converted beta carotene to vitamin A, no bony changes in the optic foramen were observed with manifest buphthalmus, high levels of beta carotene or vitamin A were unable to block the clinical development of buphthalmia, and no correlation was observed between intraocular pressure and serum vitamin A levels in rabbits fed either beta carotene or pure vitamin A.