Orbital Trauma
- The orbit is a cone-shaped bony box around the eye, and trauma can crack its thin walls, injure the globe, or trap the muscles that move the eye.
- The classic injury is the blowout fracture: a punch or ball blows out the thin orbital floor (or medial wall), often pushing fat and muscle down into the sinus below.
- The thing you must not miss is muscle entrapment — a trapped muscle is a surgical emergency, especially in kids, where the bone snaps shut like a trapdoor.
- Always hunt for the globe injury hiding behind the fracture: ruptured globe, lens dislocation, or retrobulbar hemorrhage can blind a patient while everyone admires the bone.
- CT without contrast, with thin slices and coronal reformats, is the workhorse. Skip the MRI near a possible metal foreign body.
Think of the eye as an egg sitting in an egg cup made of paper-thin bone. The egg cup looks sturdy from the front — that's the thick orbital rim you can feel under your eyebrow — but the floor and inner wall are barely thicker than a postage stamp. So when something hits the eye hard (a fist, an elbow, a baseball, an airbag), the pressure has to go somewhere, and it tends to go straight through the cheapest wall in the house.
Why the floor blows out and not the eye
Here's the elegant, slightly grim physics. When a blunt object larger than the orbital opening smacks the eye, the soft eyeball itself doesn't pop — instead, pressure spikes inside the orbit and the weakest wall gives way. The orbital floor (which is also the roof of the maxillary sinus) and the medial wall (the lamina papyracea — Latin for "paper-thin layer," and they were not exaggerating) are the usual victims.
That's a blowout fracture: the rim stays intact, but the floor breaks downward, and orbital fat — sometimes muscle — herniates into the sinus below. On a coronal CT this makes the "teardrop sign", a little blob of soft tissue hanging from the fractured floor into the dark air of the maxillary sinus, like a water droplet about to fall.
The one that ruins someone's day: entrapment
A blowout by itself usually just needs cosmetic and functional follow-up. The emergency is muscle entrapment, where the inferior rectus (the muscle that pulls the eye down) gets pinched in the fracture. The patient can't look up, sees double, and may feel nauseated — the eye is literally tethered.
This matters most in children, whose bones are bendy. The floor cracks, the muscle slips in, and then the springy bone snaps back — the "trapdoor" fracture. The CT can look almost normal because the bone sprang shut, which is exactly the trap. So believe the kid who can't look up over a CT that looks "fine."
Entrapment with a near-normal-looking CT in a child — the "white-eyed blowout" — is a true surgical emergency. The trapped muscle can necrotize within hours, and the vagal response (pain, vomiting, slow heart rate) can be mistaken for a head injury. Clinical gaze restriction beats the CT here.
Don't forget there's an eyeball in there
This is the cardinal sin of orbital trauma reads: getting hypnotized by the fracture and skating past the globe. The bone heals; a blind eye does not. Scan the globe itself every time.
| Finding | What you see on CT | Why it matters |
|---|---|---|
| Globe rupture | Misshapen ("flat tire") globe, reduced volume, abnormal contour | Sight-threatening; needs urgent ophthalmology |
| Lens dislocation | Lens displaced from its normal position | Marker of significant globe injury |
| Retrobulbar hemorrhage | Blood behind the globe, often proptosis (eye pushed forward), tenting of the back of the globe | Can cause orbital compartment syndrome — a true emergency |
| Intraocular/orbital foreign body | Dense metal or glass; wood may look like air | Changes management and rules out MRI if metallic |
A retrobulbar hematoma that stretches the optic nerve is one of the few times imaging triggers a bedside procedure. If the eye is bulging and pressure is climbing, the treatment is a lateral canthotomy to release the pressure — and it often happens before anyone finishes reading the scan. Posterior globe "tenting" (a pointed rather than round back wall) is your red flag.
How to image it
CT is the answer, and almost always non-contrast with thin slices. The single most useful trick is the coronal reformat — orbital floor and roof fractures hide on axial images but jump out when you slice top-to-bottom, because that's the plane the floor lives in.
If you suspect a wooden foreign body, lower your guard: dry wood can look like air (very dark) on CT and get dismissed as a few stray bubbles. And avoid MRI until a metallic foreign body is excluded — a magnet plus metal in the eye is exactly the horror story you'd expect.
How it fits the bigger picture
Orbital trauma rarely travels alone. The floor and medial wall are shared real estate with the sinuses and midface, so a blowout often rides along with the larger pattern of facial fractures — check whether the rim, zygoma, and maxilla are involved too. And when the orbit gets red and swollen days later without a punch, you're no longer in trauma land but thinking about orbital cellulitis instead.
The takeaway is a checklist, not a single finding: look at the walls (which one blew out), the muscles (anything trapped?), and the globe (still round, still inflated, no blood behind it?). Miss the fracture and you've missed a callback. Miss the eye and you've missed the patient.