Conjunctivitis

1. THE 2-MINUTE PHYSIOLOGY (Rapid Pathophysiology)

• The Mechanism: Conjunctivitis is defined as the inflammation or infection of the conjunctiva, the thin, transparent mucous membrane covering the inner surface of the eyelids and the anterior sclera.
• The Breakdown: The inflammatory response triggers severe vasodilation of the superficial conjunctival blood vessels, leading to the classic hyperemic "red eye" appearance. This vascular engorgement is accompanied by cellular exudation (purulent in bacterial, watery in viral), which causes the hallmark symptom of eyelids being "matted closed" upon waking.
• Epidemiological Driver: The etiology is heavily age-dependent. In pediatric patients, acute conjunctivitis is predominantly bacterial (71% bacterial vs. 16% viral). Conversely, in the adult population, the pathophysiology is overwhelmingly viral (86% viral vs. 16% bacterial).

2. THE BEDSIDE ACTION PLAN (Rapid ER Management)

• Immediate Assessment: Conjunctivitis is a benign, non-sight-threatening condition. Hemodynamic resuscitation is not required. However, the absolute paramount initial maneuver for any ocular complaint is to immediately assess and document the patient's visual acuity.
• Targeted Interventions :
• Bacterial Conjunctivitis: Treat with broad-spectrum topical ophthalmic antibiotics (e.g., Erythromycin 0.5% ointment, 0.5 inches inside the lower lid QID for 5-7 days, or Polymyxin B/Trimethoprim drops).
• Viral Conjunctivitis: Management is strictly supportive. Advise cool compresses, artificial tears, and strict hand hygiene to prevent highly contagious transmission.
• Contact Lens Wearers: You must prescribe a topical fluoroquinolone (e.g., Ciprofloxacin 0.3% ophthalmic drops) to provide mandatory coverage against Pseudomonas aeruginosa.
• Monitoring Parameters: No continuous monitoring or serial labs are indicated for uncomplicated cases.

3. THE DIAGNOSTIC GRID (Differential Diagnosis & Workup)

Top "Can't-Miss" Differentials:
Conjunctivitis is the most common cause of a red eye, but serious, vision-threatening conditions routinely mimic it.

• Acute Angle-Closure Glaucoma: Presents with severe pain, a fixed mid-dilated pupil, and a cloudy/steamy cornea.
• Bacterial Keratitis (Corneal Ulcer): A sight-threatening emergency involving infection of the cornea itself, extremely common in contact lens users.
• Anterior Uveitis (Iritis): Intraocular inflammation presenting with severe photophobia and "cell and flare" in the anterior chamber.
• Endophthalmitis: Deep intraocular infection often following surgery or penetrating trauma.

Prioritized Diagnostic Workup:

• Visual Acuity: The mandatory first step. Decreased visual acuity suggests a deeper pathology than simple conjunctivitis.
• Slit-Lamp Examination: Use a thin, bright beam at a 45-degree angle to evaluate the cornea and the anterior chamber. The anterior chamber should be clear; the presence of cells or proteinaceous material indicates uveitis, not conjunctivitis.
• Fluorescein Staining: Mandatory to rule out corneal abrasions or dendritic ulcers (Herpes Simplex Keratitis).

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

• The Clinical Visual: The resident must look for diffuse bulbar and palpebral conjunctival injection. The cornea should be crystal clear, and the pupil should be perfectly round and reactive. External Knowledge: Injection that spares the limbus (the junction of the cornea and sclera) points to conjunctivitis, whereas intense injection immediately surrounding the limbus ("ciliary flush") points to dangerous deep inflammation (uveitis/glaucoma).
• The Slit-Lamp Checklist: You must visually confirm an empty, dark anterior chamber devoid of floating white blood cells (cells) or hazy protein (flare).
• POCUS / Imaging: Point-of-care ultrasound is generally not of benefit for the evaluation of a superficial red eye unless a deeper structural issue like retinal detachment or globe rupture is suspected.

5. THE SCORING MATRIX (Risk Stratification & Guidelines)

• The Red Eye Diagnostic Algorithm: Emergency triage of the red eye relies heavily on the presence of severe pain, foreign body sensation, or limbal injection.
• Risk Triage Categories:
• Non-Urgent: Viral and Allergic Conjunctivitis.
• Urgent: Bacterial Conjunctivitis, Chlamydial Conjunctivitis, Toxic Conjunctivitis.
• Emergent: Keratitis, Scleritis, Anterior Uveitis, Hyphema, Endophthalmitis.
• Critical: Narrow Angle Glaucoma.
• Disposition: Uncomplicated viral or bacterial conjunctivitis falls into the non-urgent/urgent categories and can be safely discharged with outpatient follow-up.

6. THE DANGER ZONE (Pitfalls & Critical Actions)

• The Contact Lens Trap: Assuming a red eye in a contact lens wearer is "just conjunctivitis." Contact lens wearers are at extremely high risk for Pseudomonas bacterial keratitis (corneal ulcers).
• The Visual Acuity Trap: Failing to formally check and document visual acuity before examining or treating the eye. This is an absolute medicolegal and clinical pitfall.
• The Steroid Trap : Emergency physicians should generally never prescribe topical ocular corticosteroids for a red eye. If the patient actually has herpes simplex keratitis, steroids will cause rapid viral replication, dendritic branching, and potential globe perforation.
• Critical Action: You must document visual acuity to determine the correct treatment plan and disposition.

7. MCQ MASTERCLASS (Written Exam Tips)

• Buzzword: "Eyelids matted closed upon waking" = Bacterial Conjunctivitis.
• Buzzword: "Red eye in a contact lens wearer" = Think Pseudomonas and prescribe topical Ciprofloxacin.
• Epidemiology Fact: Children overwhelmingly get bacterial conjunctivitis (71%), while adults overwhelmingly get viral conjunctivitis (86%).
• Distractor Options: Exam questions will describe a "red, painful eye with photophobia and hazy cornea." The distractors will include "Bacterial Conjunctivitis" or "Viral Conjunctivitis." The correct answer is Acute Angle-Closure Glaucoma or Anterior Uveitis, because simple conjunctivitis does not typically cause a hazy cornea, severe deep pain, or extreme photophobia.

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

"I am evaluating a patient presenting with an acute red eye. My first critical action was obtaining and documenting a normal visual acuity. The patient complains of crusting and irritation but denies deep, severe pain, severe photophobia, or vision changes, making acute angle-closure glaucoma and uveitis less likely. On physical exam, I note diffuse conjunctival injection without ciliary flush. My slit-lamp examination reveals a clear cornea without fluorescein uptake, ruling out keratitis and abrasions, and a clear anterior chamber devoid of cell and flare, ruling out anterior uveitis. Given the purulent discharge and matted eyelids, this is highly consistent with acute bacterial conjunctivitis. I will discharge the patient with broad-spectrum topical ophthalmic antibiotics, strict return precautions for worsening pain or vision loss, and advise them on strict hand hygiene to prevent transmission."