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Ocular Trauma · Foreign Body & Metallosis

Metallosis Syndromes

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  1. Siderosis Bulbi
  2. Chalcosis
  3. Electroretinography in Siderosis Bulbi
  4. Related Topics

Siderosis Bulbi

Chronic retention of an iron-containing intraocular foreign body leads to a toxic condition called siderosis bulbi. Iron ions catalyze free radical formation that damages the retina, lens, and trabecular meshwork, producing progressive pigmentary and functional changes throughout the eye. Left in place, a retained iron IOFB is not an inert bystander — it actively destroys the tissue around it over weeks to months.

Chalcosis

A retained copper-containing intraocular foreign body produces a different clinical picture: chalcosis. Copper deposition in ocular tissues causes a greenish-brown iris discoloration along with heterochromia and characteristic lens changes, distinct from the iron-related findings of siderosis. Clinically, chalcosis presents with heterochromia, mydriasis, and greenish iris discoloration.

The signature finding of chronic chalcosis is a distinctive lens opacity called a sunflower cataract. Copper deposits accumulate in the anterior and posterior lens capsule in a radiating, petal-like pattern, producing the characteristic sunflower appearance — one of the more visually distinctive and high-yield findings in all of ocular trauma.

Copper concentration matters clinically, not just "it's copper." A foreign body that is mostly pure metallic copper (roughly >85% copper) tends to trigger a violent, acute suppurative reaction — potentially progressing to panophthalmitis and loss of the eye — rather than the slower chalcosis described above. Chalcosis, with its more indolent course and sunflower cataract, is instead typical of copper alloys with lower copper content, such as brass or bronze (<85% copper). The exact composition of a retained copper-containing IOFB is therefore part of what determines whether it behaves like an acute surgical emergency or a slowly evolving toxic process.

Electroretinography in Siderosis Bulbi

Electroretinography (ERG) is both a diagnostic and monitoring tool in siderosis bulbi, and it follows a classic, testable pattern over time: early siderosis can transiently increase ERG amplitude due to retinal irritation, followed by a progressive decline and eventual extinction of the response as iron toxicity destroys the photoreceptors. In other words, the b-wave doesn't just fall from the start — it can paradoxically rise first, which is a detail worth remembering specifically because it's counterintuitive.

High-Yield
  • Iron IOFB → siderosis bulbi. Copper IOFB → chalcosis. Don't mix up which metal causes which syndrome.
  • Sunflower cataract is the classic lens finding of chalcosis, from copper deposition in a radiating pattern on the lens capsule.
  • Siderosis bulbi's ERG signature: amplitude initially increases from retinal irritation, then progressively declines to extinction as toxicity worsens.
  • Pure metallic copper provokes a more severe, sight-threatening reaction than iron or copper alloys with lower copper content.

Continue exploring Ocular Trauma:

Intraocular Foreign Body Orbital Fractures Orbital Compartment Syndrome & Retrobulbar Hemorrhage Sympathetic Ophthalmia

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