Urgent CT Orbits Without Contrast is the Essential First Imaging Study
A patient with diplopia after flash-bang exposure requires immediate CT orbits without contrast to evaluate for orbital fracture, globe injury, extraocular muscle entrapment, and intraorbital foreign bodies 1. This is a traumatic orbital injury until proven otherwise, and CT is the most accurate method for detecting fractures and assessing soft tissue damage 1.
Immediate Clinical Assessment
Focus your examination on these specific findings that indicate severity:
- Periorbital swelling and ecchymosis - present in 89.9% of patients with actual ocular injuries 2
- Diplopia pattern - binocular diplopia (resolves when one eye is closed) suggests orbital/muscle injury rather than monocular causes 3
- Restriction of ocular movement - particularly upward gaze limitation, which may indicate inferior rectus entrapment in a "trap door" fracture 1
- Visual acuity - any decrease suggests globe or optic nerve injury 1
- Pupillary response - assess for afferent pupillary defect
- Subconjunctival hemorrhage or hyphema - signs of globe trauma 1
Imaging Protocol
CT orbits without contrast is the gold standard 1. The ACR Appropriateness Criteria (2024) designate this as "usually appropriate" for traumatic visual complaints with suspected orbital injury 1.
Why CT Orbits Specifically:
- 94.9% sensitive for intraorbital foreign bodies (metallic or glass) 1
- Most accurate for detecting fractures 1
- Identifies soft tissue injuries including globe rupture and extraocular muscle damage 1
- Detects hemorrhage and herniation of orbital contents 1
Add CT Head If:
- Suspected intracranial injury or altered mental status
- Orbital roof fracture suspected (more common in younger patients and associated with traumatic brain injury) 1
Contrast-enhanced CT is NOT indicated for initial evaluation 1. Plain CT provides all necessary information for acute traumatic orbital injury.
Critical Pitfalls to Avoid
Do not dismiss diplopia as minor soft tissue swelling alone. While hematoma and swelling can cause diplopia, you must rule out:
- Trap door fractures with muscle entrapment - these cause rapid ischemic injury to the extraocular muscle, leading to permanent restrictive strabismus if not identified early 1
- Open globe injury - can result from blunt trauma (rupture) or penetrating injury 1
- Optic nerve injury - suggested by visual field defects or decreased acuity 1
The absence of obvious external trauma does not exclude serious injury. Flash-bang devices can cause both blast injury and blunt trauma from the device itself.
Urgent Referral Indications
Based on recent ED data, 42% of diplopia patients required urgent etiological treatment and 31% needed hospitalization 3. Immediate ophthalmology consultation is needed for:
- Any suspicion of open globe injury
- Significant restriction of eye movement
- Decreased visual acuity
- Abnormal pupillary responses
- CT findings of orbital fracture with muscle entrapment
- Intraorbital foreign body
Time-Sensitive Considerations
Imaging should be performed immediately, not delayed 4. In a 2023 study, 88.3% of diplopia patients received neuroimaging, with 75.7% imaged the same day 4. The high rate of urgent treatments (42%) underscores that diplopia is not a benign symptom 3.
For patients with penetrating injuries or specific ocular presentations (periorbital swelling, diplopia), ophthalmology consultation should be prioritized 2. In blunt trauma cases with diplopia, 26.1% had confirmed ocular injuries requiring intervention 2.
Why MRI is NOT First-Line
While MRI provides superior soft tissue contrast, it is supplementary to CT in acute orbital trauma 1. CT is faster, more readily available in emergency settings, and superior for detecting fractures and foreign bodies. MRI has no established role in initial evaluation of orbital trauma per ACR guidelines 1.