Orbital Anatomy & Basics - Bony Box Blueprint
- Structure: 4-sided pyramid; Volume: 30 mL. Apex points posteromedially.
- Orbital Bones (7): 📌 "Many Friendly Zebras Enjoy Lazy Summer Picnics"
- Frontal, Sphenoid, Zygomatic, Maxilla, Lacrimal, Ethmoid, Palatine.
- Key Walls & Features:
- Roof: Frontal, Sphenoid (lesser wing).
- Floor: Maxillary, Palatine, Zygomatic.
- Medial: Ethmoid (lamina papyracea - thinnest), Lacrimal, Maxillary, Sphenoid.
- Lateral: Zygomatic, Sphenoid (greater wing) - strongest.
⭐ The posteromedial orbital floor (maxillary bone) is the weakest part, prone to blowout fractures.
Orbital Fractures - Crack-Up Cases
Blunt trauma often causes orbital fractures. Key types:
| Fracture Type | Bones Involved | Key Features | Imaging Sign(s) |
|---|---|---|---|
| Blowout | Floor (maxillary), Medial wall (ethmoid) | Diplopia (esp. up/downgaze), Enophthalmos >2mm, Infraorbital anesthesia, Restricted EOM (inf. rectus) | 'Teardrop', 'Hanging drop' |
| Tripod (ZMC) | Zygoma (arch, body, orbital rim), Maxilla | Malar flattening, Trismus, Infraorbital anesthesia, Palpable step-off | 'Floating zygoma' |
| NOE | Nasal, Ethmoid, Lacrimal, Medial orbital rim | Telecanthus (MCT injury), Nasal bridge depression/widening, CSF rhinorrhea, Epiphora. 📌 NOE = Nose Out Everywhere | Disrupted Medial Canthal Tendon (MCT) |
⭐ 'Teardrop sign' on CT scan is characteristic of an orbital floor blowout fracture with herniation of orbital contents into the maxillary sinus.
Penetrating Injuries & FBs - Eye Spy Intruders
- History: Sharp/high-velocity trauma. Signs: Entry wound, ↓vision, pain, diplopia.
- Always assess globe integrity (e.g., Seidel test for perforation).
- ⭐ > MRI is contraindicated if a metallic intraorbital foreign body (IOFB) is suspected; CT is the investigation of choice (IOC).
- Investigations:
- CT scan (orbit): IOC, esp. for metallic/bony FBs. 📌 NO MRI for Metallic Intruders!
- X-ray: Radio-opaque FBs.
- B-scan USG: Non-metallic FBs, posterior segment.
- Management:
- Tetanus prophylaxis, broad-spectrum IV antibiotics.
- Surgical exploration & FB removal (consider material: inert vs. organic).
Clinical Evaluation & Management - Trauma Triage Tactics
- Initial Assessment:
- History (mechanism), VA, pupils (RAPD), IOP.
- Motility, proptosis/enophthalmos, palpation (crepitus, step-offs), globe integrity.
- Key Investigations:
- CT scan (orbit/brain): Gold standard for fractures, FBs.
- MRI: Optic nerve/soft tissue (NO metallic FB).
- Management Priorities:
- ⚠️ Emergencies:
- OCS/RBH: 📌 P.A.I.N.: Proptosis, Periorbital swelling, Afferent Pupillary Defect, Increased IOP (>40 mmHg), Ophthalmoplegia, Numbness. Immediate lateral canthotomy & cantholysis.
- Penetrating Globe Injury: Shield, NPO, IV Abx, tetanus, surgery.
- Urgent: Fractures (entrapment), optic neuropathy.
- ⚠️ Emergencies:
⭐ Orbital Compartment Syndrome (OCS) is an ophthalmic emergency requiring immediate lateral canthotomy and cantholysis to prevent irreversible vision loss.
High‑Yield Points - ⚡ Biggest Takeaways
- Blowout fractures most commonly involve the orbital floor, causing diplopia (especially on upgaze) and enophthalmos.
- Orbital emphysema, air in the orbit from sinus communication, presents with eyelid swelling and crepitus.
- Retrobulbar hemorrhage is an emergency: proptosis, ↑IOP, RAPD, vision loss; treat with lateral canthotomy & cantholysis.
- Traumatic Optic Neuropathy (TON) causes acute visual loss and RAPD post-trauma; steroids controversial.
- CT scan (axial and coronal views) is crucial for diagnosing orbital fractures and associated injuries.
- Carotid-Cavernous Fistula (CCF) can present post-trauma with pulsatile exophthalmos, bruit, and chemosis.
- Always rule out globe rupture in severe orbital trauma; signs include uveal prolapse, ↓vision, and abnormal anterior chamber depth.
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