Ocular Trauma & Chemical Burns
A high-yield Step 2 CK review of ocular trauma and chemical burns organized around next-best-step triage: irrigate chemical burns immediately, shield a suspected open globe, and recognize hyphema, orbital blowout fracture, and retrobulbar hemorrhage by their buzzwords and management.
Ocular trauma is a do-not-miss Step 2 CK topic, and it is almost always tested as a next-best-step decision rather than a diagnosis. Two reflex answers dominate the exam. First, a chemical splash → irrigate immediately — copious irrigation comes before visual acuity, before history, before any detailed exam. Second, a suspected open (ruptured) globe → place a rigid shield and stop manipulating the eye; give systemic antibiotics, keep the patient NPO, and get urgent ophthalmology. The remaining injuries each carry a signature buzzword and a triage move: hyphema (blood in the anterior chamber), orbital blowout fracture (diplopia + cheek numbness), retrobulbar hemorrhage (proptosis + a tight orbit), and corneal abrasion (fluorescein uptake). Learn the buzzword, then the decision.
- First step for any chemical burn = immediate copious irrigation with saline/LR (or plain water if unavailable); do NOT wait for visual acuity or history.
- Irrigate ≥15–30 min; check pH and continue until pH is neutral (~7.0–7.4) and stable. Then sweep the fornices to remove retained particulate (e.g., lime/cement).
- Alkali burns are worse than acid — bases cause liquefactive necrosis and penetrate deeply into the anterior chamber; acids cause coagulative necrosis that self-limits (exception: hydrofluoric acid penetrates like an alkali).
- Alkali sources: lye, ammonia, drain/oven cleaner, lime/plaster/cement, airbag powder. Acid sources: car battery (sulfuric), hydrochloric, hydrofluoric.
- Perilimbal blanching/whitening = limbal ischemia = poor prognosis (loss of limbal stem cells → corneal scarring and neovascularization).
- After irrigation: topical antibiotic, cycloplegic, topical steroid (early, short course — taper by ~10 days to avoid melting), preservative-free tears; ascorbate/citrate to limit corneal melting. Urgent ophthalmology referral.
Alkali vs. acid burns
| Feature | Alkali (base) burn | Acid burn |
|---|---|---|
| Necrosis | Liquefactive | Coagulative |
| Penetration | Deep, rapid — into anterior chamber | Superficial, self-limited (protein barrier) |
| Severity | Worse | Usually milder |
| Classic sources | Lye, ammonia, lime/cement, drain & oven cleaner, airbag | Sulfuric (car battery), hydrochloric, acetic |
| Exception | — | Hydrofluoric acid penetrates like an alkali |
| First step (both) | Immediate copious irrigation until pH neutral | Immediate copious irrigation until pH neutral |
Vignette: A construction worker splashes wet cement into his eye. He has severe pain, tearing, and blepharospasm; the cornea looks hazy and there is perilimbal whitening.
Diagnosis: Alkali (calcium hydroxide) chemical burn — the limbal ischemia signals a serious injury.
Next best step: Immediate copious irrigation with saline/LR, using a topical anesthetic and lid speculum — before checking visual acuity. Irrigate until the pH normalizes (~7.0–7.4), then sweep the fornices for retained lime particles. Only after irrigation do you complete the exam and start topical antibiotic, cycloplegic, and a short course of steroid, with urgent ophthalmology referral. Do not delay irrigation to obtain a history or imaging.
- Open/ruptured globe — buzzwords: teardrop/peaked pupil, positive Seidel sign (fluorescein streams from the wound), 360° subconjunctival hemorrhage, low IOP, uveal prolapse, metal-on-metal history.
- Open-globe management: rigid eye shield (no patch, no pressure); no tonometry or drops; NPO, antiemetics, elevate head, tetanus, systemic (IV) antibiotics, CT orbit (avoid MRI if metallic FB); urgent surgical repair.
- Hyphema (blood in anterior chamber): elevate head 30–45°, rigid shield, limit activity, avoid aspirin/NSAIDs, cycloplegic, monitor IOP (corneal blood staining risk). Screen for sickle cell/trait — sickled cells clog the trabecular meshwork; avoid acetazolamide/CAIs. Rebleed peaks days 2–5.
- Retrobulbar hemorrhage (orbital compartment syndrome): proptosis, tight orbit, ↓vision, RAPD, ↑IOP → emergent lateral canthotomy + cantholysis (clinical dx — do NOT wait for CT).
- Orbital blowout fracture: diplopia on upgaze, restricted upgaze, enophthalmos, infraorbital (V2) cheek/lip numbness; CT is the test.
Vignette: A man was hammering metal when something struck his eye. Vision is blurred; the pupil is peaked (teardrop-shaped), there is a subconjunctival hemorrhage, and fluorescein shows a stream of aqueous diluting the dye (positive Seidel sign). IOP is low.
Diagnosis: Open (ruptured) globe, likely with an intraocular foreign body.
Next best step: Place a rigid eye shield and stop examining the eye — no tonometry, no pressure, no topical ointments. Keep the patient NPO, give antiemetics and systemic broad-spectrum antibiotics (endophthalmitis prophylaxis), update tetanus, elevate the head, and order a CT orbit (thin cuts; avoid MRI given possible metal). Obtain urgent ophthalmology for surgical repair. Avoid B-scan ultrasound (applies pressure).
Vignette: A 12-year-old is hit in the eye with a baseball. The eye looks white and quiet, but he cannot look up, and he becomes bradycardic and nauseated/vomiting whenever he tries to move the eye. CT shows an orbital floor fracture with soft tissue herniating into the maxillary sinus.
Diagnosis: Pediatric "white-eyed" trapdoor blowout fracture with inferior rectus entrapment triggering the oculocardiac reflex (bradycardia–nausea with eye movement).
Next best step: Urgent surgical release (within ~24–48 h) — entrapment with the oculocardiac reflex is a surgical emergency to prevent muscle ischemia/necrosis. Contrast this with the typical adult blowout (enophthalmos, V2 numbness, minimal entrapment), usually repaired electively at 1–2 weeks. Tell all patients to avoid nose-blowing (risk of orbital emphysema).
Chemical burn — "Irrigate before you investigate." Irrigation precedes visual acuity, history, and imaging in every chemical eye burn.
Alkali penetrates "All the way." Alkali → liquefactive necrosis → deep penetration → worse prognosis; Acid → coAgulative necrosis → self-limited (hydrofluoric is the exception).
Open globe — "Shield it, don't feel it." Rigid shield, no patch/pressure, no drops, NPO, systemic antibiotics, CT, urgent ophthalmology.
Hyphema + Sickle → Skip Acetazolamide. Systemic carbonic anhydrase inhibitors promote sickling (acidosis/lower aqueous pH); sickled cells obstruct the trabecular meshwork and spike IOP — so avoid them in sickle-cell patients with hyphema.
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