CT Orbit Without Contrast
For an air rifle injury to the eye near the medial canthus with a visible entry site, CT orbit without contrast is the most appropriate investigation to assess for foreign body, fractures, and intraorbital damage. 1, 2
Rationale for CT Orbit as First-Line Imaging
Non-contrast thin-section orbital CT with multiplanar reconstructions is the gold standard for evaluating orbital trauma, providing excellent anatomic definition and superior capability for identifying osseous integrity, fractures, and displaced fragments 3, 1
CT has 94.9% sensitivity for detecting intraorbital foreign bodies, especially metallic ones, which is critical in this air rifle injury where a projectile may be retained 1, 2
Contrast is not needed in the trauma setting and would only delay diagnosis without adding clinically relevant information 3, 1, 2
Critical Assessment Points
The proximity to the medial canthus raises specific concerns that CT will address:
- Medial orbital wall fractures (the thinnest orbital wall, most vulnerable to injury) 3
- Retained foreign body localization (air rifle pellet or fragments) 2
- Optic nerve integrity (given the trajectory near the medial orbit) 4
- Extraocular muscle involvement or entrapment 4
- Intraorbital hemorrhage or emphysema 4
Why Other Options Are Inappropriate
MRI (option a) is contraindicated when metallic foreign bodies are suspected due to potential movement of the object caused by the magnetic field 3, 2
CT angiogram (option c) is not indicated as initial imaging for orbital trauma; vascular imaging is reserved for suspected vascular injury in the larger context of facial/intracranial trauma, not isolated orbital penetration 3
Plain X-ray (option d) is insufficient for detecting orbital pathology and has been supplanted by CT 3, 1
Reassurance (option e) is dangerous given the penetrating mechanism, visible entry site, and risk of retained foreign body, infection, or occult globe rupture 2
Common Pitfalls to Avoid
Do not delay imaging to "watch and wait" despite preserved vision—occult injuries including retained foreign bodies, small fractures, or delayed hemorrhage can cause devastating complications 4
Do not manipulate the eye or apply pressure until imaging is complete and ophthalmologic assessment is performed 2
Ensure urgent ophthalmology consultation accompanies the CT order, as penetrating orbital trauma requires specialist evaluation regardless of imaging findings 2