Uveitis

1. THE 2-MINUTE PHYSIOLOGY (Rapid Pathophysiology)

• The Mechanism: Uveitis is an emergent, vision-threatening inflammation of the uveal tract (which consists of the iris, ciliary body, and choroid). Most cases seen in the ED are anterior uveitis (iritis or iridocyclitis).
• The Cellular Breakdown: Inflammation, secondary to trauma, infection, or systemic autoimmune disease, causes a breakdown of the blood-aqueous barrier (External Knowledge). This allows protein exudate ("flare") and white blood cells ("cells") to leak directly into the anterior chamber of the eye.
• The Pain Generator : The severe, deep aching pain and hallmark photophobia are mechanically driven by inflammatory spasm of the ciliary body muscles and the iris sphincter.
• The Systemic Link: The condition is highly associated with systemic autoimmune disorders, most notably those linked to the HLA-B27 gene (e.g., Ankylosing Spondylitis, Reactive Arthritis, and Inflammatory Bowel Diseases like Crohn's disease).

2. THE BEDSIDE ACTION PLAN (Rapid ER Management)

• The Vital Sign of the Eye: The mandatory, absolute first step before any diagnostic maneuvers, lights, or drops is to obtain and formally document baseline visual acuity.
• Intraocular Pressure (IOP) Check: You MUST measure the IOP using tonometry to definitively rule out acute angle-closure glaucoma before administering any pupil-dilating drops.
• Ciliary Spasm Relief: If IOP is normal (≤20 mm Hg), administer Cyclopentolate 1% (2 drops). This is a cycloplegic/mydriatic agent that paralyzes the ciliary body, providing profound pain relief from the ciliary spasm and preventing the formation of synechiae (adhesions between the iris and lens).
• First-Line Anti-inflammatory Therapy: The mainstay of definitive treatment is topical corticosteroids to halt the immune response. Options include Prednisolone acetate 1% (every 1–6 hours) or Dexamethasone 0.1% (1 drop every 30–60 minutes). Note: These must strictly be initiated ONLY after discussion with Ophthalmology.

3. THE DIAGNOSTIC GRID (Differential Diagnosis & Workup)

Top "Can't-Miss" Differentials:

• Acute Angle-Closure Glaucoma: Both present with a painful red eye, but glaucoma features elevated IOP (>20 mm Hg), a fixed mid-dilated pupil, and a steamy cornea.
• Endophthalmitis: A devastating, deep infection of the globe (often presenting with a hypopyon) that is typically a complication of recent ocular surgery or penetrating trauma.
• Bacterial Keratitis / Corneal Ulcer: Presents with severe pain and redness, but fluorescein staining will reveal a distinct corneal epithelial defect.
• Conjunctivitis: A superficial infection that causes diffuse redness but typically spares the limbus (the junction of the cornea and sclera) and lacks deep pain or severe photophobia.

Prioritized Diagnostic Workup:

• Tonometry: Mandatory to rule out concomitant or mimicking glaucoma.
• Slit-Lamp Examination: The gold-standard diagnostic modality in the ED to visualize anterior chamber inflammation.
• Systemic Labs: Routine ED lab work is generally unnecessary for isolated, first-time cases, but an outpatient rheumatologic/autoimmune workup (e.g., HLA-B27, ESR/CRP) may be indicated upon follow-up.

4. THE VISUAL BOARD (ECG / POCUS / Imaging)

• The Slit-Lamp Checklist: You must perform a slit-lamp examination in a darkened room using a high-intensity, 1mm conical beam. Look for:
• Limbal Injection (Ciliary Flush): A distinct ring of deep, violaceous hyperemia immediately surrounding the cornea (the limbus), as opposed to the diffuse redness of simple conjunctivitis.
• Cells: Floating white dots in the anterior chamber representing individual white blood cells (External Knowledge: Often described as looking like dust motes in a projector beam).
• Flare: A hazy, smoky appearance to the aqueous humor caused by suspended protein exudate.
• Hypopyon: In severe cases, white blood cells and pus will precipitate and form a visible fluid level at the bottom (inferior aspect) of the anterior chamber.

5. THE SCORING MATRIX (Risk Stratification & Guidelines)

• Triage Criteria: Uveitis is strictly categorized as an ocular emergency due to the high risk of permanent visual impairment from synechiae, cataracts, or secondary glaucoma.
• Consultation Guidelines: All patients diagnosed with anterior uveitis or a hypopyon require an urgent ophthalmology consultation while in the ED.
• Disposition: Reliable patients without vision loss or severe complications can often be discharged after the ophthalmologist determines the exact frequency of corticosteroid drops (ranging from every 1 to 6 hours) and arranges close outpatient follow-up (usually within 24-48 hours).

6. THE DANGER ZONE (Pitfalls & Critical Actions)

• The Dilating Trap: Administering cycloplegic drops (like cyclopentolate) for pain control before checking the IOP. Critical Action: Board examiners mandate that you rule out acute angle-closure glaucoma with tonometry first, as dilating an eye with narrow angles will precipitate a blinding glaucoma crisis.
• The Steroid Trap: Prescribing topical corticosteroids on your own. Critical Action: Corticosteroids carry a high risk of worsening undiagnosed Herpes Simplex keratitis and causing IOP spikes. They must only be initiated in the ED after direct consultation with an ophthalmologist.
• The "Pink Eye" Dismissal: Mistaking the limbal injection (ciliary flush) of uveitis for the diffuse redness of viral/allergic conjunctivitis, leading to an inappropriate discharge without steroids or a slit-lamp exam.

7. MCQ MASTERCLASS (Written Exam Tips)

• Buzzwords: "Limbal injection," "Ciliary flush," "Cells and flare in the anterior chamber," "Deep aching eye pain with photophobia."
• Systemic Associations: If a question describes a young male with lower back pain (Ankylosing Spondylitis / HLA-B27) or a patient with chronic diarrhea (Crohn's disease) presenting with a painful red eye, the diagnosis is Anterior Uveitis.
• Distractor Trap: A question stem will ask you to identify features of Uveitis and offer "diffuse eye redness that spares the limbus" as an option. Do not pick this. Redness that spares the limbus is classic for simple conjunctivitis; Uveitis specifically causes limbal injection.

8. THE BOARDROOM SCRIPT (OSCE & Oral Board Tips)

"Examiner, my patient presents with a painful red eye, tearing, and severe photophobia. My immediate first step is to formally document their baseline visual acuity. On physical exam, I note a distinct limbal injection (ciliary flush). I will perform a detailed slit-lamp examination looking for 'cells and flare' or a hypopyon in the anterior chamber. Before administering any mydriatic agents, I will perform tonometry to ensure the IOP is normal and rule out acute angle-closure glaucoma. Given the diagnosis of anterior uveitis, I will instill 2 drops of Cyclopentolate 1% to break the ciliary spasm and provide pain relief. Because this is a vision-threatening emergency, I will urgently consult ophthalmology while the patient is in the ED, and I will only initiate topical corticosteroids, such as Prednisolone acetate 1%, after confirming the plan and follow-up timeline with the consultant."