Question:medium
A boy working on a hammer & chisel had a foreign body entering his eye. Which investigation is detrimental (contraindicated) for this boy?
A boy working on a hammer & chisel had a foreign body entering his eye. Which investigation is detrimental (contraindicated) for this boy?
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A magnetic field is dangerous in the presence of metallic intraocular foreign bodies.
Updated On: Jun 23, 2026
- X-ray
- B scan orbit
- CT Scan
- MRI
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The Correct Option is D
Solution and Explanation
Mechanism of injury: hammer striking a chisel generates high-velocity metallic fragments. The foreign body is therefore metallic and likely ferromagnetic.
MRI is contraindicated in this scenario because the strong static magnetic field of the MRI scanner will exert translational force and torque on ferromagnetic metallic objects. Inside the eye, this can cause the fragment to move and lacerate the retina, choroid, or optic nerve, leading to permanent vision loss or globe rupture.
Safe alternatives for localising intraocular foreign bodies:
- X-ray orbit: quick, detects radiodense (metallic) objects
- CT orbit: gold standard -- detects both metallic and non-metallic foreign bodies, provides 3D localisation without magnetic risk
- B scan ultrasound: useful when X-ray/CT unavailable, but use with caution in open globe \[\boxed{\text{MRI -- contraindicated in metallic IOFB}}\]
MRI is contraindicated in this scenario because the strong static magnetic field of the MRI scanner will exert translational force and torque on ferromagnetic metallic objects. Inside the eye, this can cause the fragment to move and lacerate the retina, choroid, or optic nerve, leading to permanent vision loss or globe rupture.
Safe alternatives for localising intraocular foreign bodies:
- X-ray orbit: quick, detects radiodense (metallic) objects
- CT orbit: gold standard -- detects both metallic and non-metallic foreign bodies, provides 3D localisation without magnetic risk
- B scan ultrasound: useful when X-ray/CT unavailable, but use with caution in open globe \[\boxed{\text{MRI -- contraindicated in metallic IOFB}}\]
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