When various doses of iron powder, ferrous chloride, ferric chloride and ferric oxide were injected into the vitreous of squirrel monkey eyes, the ferric form proved less toxic than the others. The retinal changes were visible ophthalmoscopically as geographic confluent patches of whitened retina and disturbed pigment epithelium. The iron affected the ERG within the first few hours, and selective damage of receptor cells and retinal pigment epithelium was evident morphologically at four hours. A secondary edema appeared in the inner retinal layers by 24 hours and resolved over the next few days. In later stages, pigment epithelial cells and macrophages from other sources phagocytosed the destroyed receptor cells and some of the intravitreal iron. Bruch's membrane and the choroid, as well as the inner retinal layers were unaffected. At least two ERG changes were recognized-a reversible diminution in amplitude apparently related to the transient edema of the inner retina, and a permanent diminution of amplitude related to receptor cell damage. A third change reported by others, a transient increase in ERG amplitude, was an indefinite finding in this study. When vitreous haze was low enough to permit it, fluorescein angiography demonstrated the pigment epithelial defects and showed the retinal edema present in the first days after iron injection.
ASJC Scopus subject areas