Myelin oedema, optic neuropathy and retinopathy in experimental Stypandra imbricata toxicosis.

Rats experimentally poisoned with the toxic plant Stypandra imbricata developed acute oedema of central and peripheral myelin and extensive axonal degeneration in the optic nerves. The oedema developed with vacuolation and splitting of myelin lamellae at the intraperiod line. Following recovery from acute intoxication, myelin oedema resolved after 6 to 12 weeks, but severe retinal degeneration and optic nerve atrophy remained. Morphological abnormalities in glial cells and axons were only found in the optic nerves. It was concluded that there is probably also a direct toxic effect on the axons of the optic nerve and the photoreceptor cells of the retina. The chemical nature of the toxin remains to be defined but the marked similarity of its toxic effects to those of hexachlorophene are noted.