Differential Diagnosis for Rust Ring Eye

• Single most likely diagnosis
  • Iron foreign body: This is the most common cause of a rust ring in the eye, which occurs when a metallic foreign body, especially one containing iron, penetrates the cornea and leaves a deposit of iron oxide, leading to the formation of a rust ring.
• Other Likely diagnoses
  • Corneal siderosis: This condition can also lead to the deposition of iron in the cornea, although it is less likely to cause a distinct rust ring compared to an iron foreign body.
  • Traumatic corneal injury: Any significant trauma to the cornea can potentially lead to the introduction of foreign material, including iron, into the corneal tissue.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Intraocular foreign body: While less common than corneal foreign bodies, an intraocular foreign body, especially if made of iron, can lead to severe complications, including siderosis bulbi, which can result in vision loss and even loss of the eye.
  • Endophthalmitis: This is a severe infection within the eye that can be caused by a penetrating injury, including one that introduces a foreign body into the eye. Prompt diagnosis and treatment are crucial to prevent vision loss.
• Rare diagnoses
  • Corneal tattoo: Although rare, a corneal tattoo using iron-based ink could potentially mimic the appearance of a rust ring.
  • Siderosis from systemic sources: In rare cases, systemic conditions leading to iron overload (e.g., hemochromatosis) could potentially deposit iron in the cornea, although this would be an extremely rare cause of a rust ring appearance.