An intraocular foreign body composed of iron can result in siderosis. The iron ions are absorbed intracellularly, resulting in epithelial toxicity. If the foreign body is not removed there will eventually be severe deterioration of visual function.
Anatomic Site
Clinical Finding in Siderosis
cornea
normal or diffuse brown haze
iris
rusty brown discoloration in the affected eye
lens
diffuse brownish discoloration of the anterior capsule; cortex appears yellow; a cataract may develop
vitreous fluid
brownish discoloration with opacification
retina
epithelial degeneration affects peripheral fundus first, then posterior segment
Other features:
(1) The deposits are attracted to a magnet, which can aid in removal.
(2) The electroretinogram (ERG) initially shows a supernormal b-wave. Over time there is a 100% loss in amplitudes. Tacking the changes over time is useful for monitoring retained iron bodies.
(3) Secondary glaucoma may develop late.
Prognosis is affected by:
(1) whether the foreign body is removed
(2) ferrous state (more toxic than ferric)
(3) vitreous opacities
(4) diffuse cataract
(5) retinal toxicity
(6) secondary glaucoma
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