Endophthalmitis

1. THE 2-MINUTE PHYSIOLOGY (Rapid Pathophysiology)

• The Mechanism: Endophthalmitis is a severe, sight-threatening purulent inflammation of the intraocular fluids (vitreous and aqueous humor).
• The Breakdown: It is primarily an infectious process divided into two pathophysiological pathways:
• Exogenous (Most Common): Direct inoculation of bacteria or fungi into the normally sterile intraocular space from an outside source. This is heavily driven by recent eye surgery, intravitreal injections, or penetrating ocular trauma.
• Endogenous: Hematogenous seeding of the eye from a distant primary infection. If the patient is systemically ill, the endophthalmitis is likely secondary to an endogenous source of bacteremia or sepsis.
• The Result: The infection triggers massive leukocytic infiltration into the vitreous and anterior chamber, leading to the clinical hallmarks of hazy intraocular media, blunting of the red reflex, and rapid, irreversible retinal destruction.

2. THE BEDSIDE ACTION PLAN (Rapid ER Management)

• Immediate Assessment: Endophthalmitis in isolation is an ocular emergency but not a life-threatening illness. However, if the patient presents with systemic toxicity, immediately resuscitate for sepsis (IV fluids, vasopressors, broad-spectrum antibiotics) driven by the endogenous bacteremic source.
• Targeted Interventions:
• Consultation: The paramount ED intervention is an urgent ophthalmology consultation in the ED for definitive diagnostic tapping and therapy.
• Positioning (External Knowledge): Keep the head of the bed elevated to 30-45 degrees to allow inflammatory cells to settle dependently in the anterior chamber (hypopyon), clearing the visual axis.
• Pain & Nausea Control : Administer aggressive IV antiemetics (e.g., Ondansetron 4 mg IV) and analgesia. Vomiting spikes intraocular pressure, which can worsen ocular damage or cause extrusion if there is an associated unhealed surgical wound or trauma.
• First-Line Medications : The definitive treatment requires intravitreal antibiotics injected directly into the eye by an ophthalmologist (typically Vancomycin 1 mg/0.1 mL + Ceftazidime 2.25 mg/0.1 mL). Systemic IV antibiotics (e.g., IV Vancomycin and Ceftriaxone) are strictly indicated if an endogenous (bacteremic) source is suspected.

3. THE DIAGNOSTIC GRID (Differential Diagnosis & Workup)

Top "Can't-Miss" Differentials:
The diagnostic algorithm for a red and painful eye categorizes endophthalmitis as an "Emergent" diagnosis. It must be differentiated from:

• Acute Angle-Closure Glaucoma: A "Critical" diagnosis presenting with a fixed, mid-dilated pupil, steamy cornea, and markedly elevated intraocular pressure.
• Anterior Uveitis: Intraocular inflammation often with a hypopyon.
• Bacterial Keratitis: An infection/ulcer of the cornea itself, common in contact lens users.
• Hyphema: Blood in the anterior chamber, usually traumatic.

Prioritized Diagnostic Workup:

• Visual Acuity: The mandatory first step for any eye complaint. Endophthalmitis causes blurry or lost vision in 94% of patients and severe vision loss in 26%.
• History & Physical: Ask specifically about the two major risk factors: recent eye surgery/injections (exogenous) or recent generalized infections/IV drug use (endogenous bacteremia). Look for acute progressive monocular pain (74%), a "red eye" (82%), and eyelid swelling (34%).
• Slit-Lamp Examination: Perform a complete ocular exam looking for hazy intraocular media (present in 79%) and a blunted red reflex.
• Sepsis Workup: If the patient is systemically ill, obtain blood cultures, lactate, and a complete metabolic panel to hunt for the endogenous source.

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

• The Clinical Visual: The resident must look for intense conjunctival injection with a hazy, cloudy anterior chamber. A classic physical exam finding is the blunting or complete absence of the red reflex when viewed with an ophthalmoscope due to dense vitreal inflammation.
• The Slit-Lamp Checklist: Look for a hypopyon (External Knowledge)—a visible layer of white, purulent exudate resting dependently in the bottom of the anterior chamber.
• POCUS View : On ocular point-of-care ultrasound (B-mode), a normal vitreous is completely black (anechoic). In endophthalmitis, you will see highly echogenic (white) mobile debris floating in the vitreous chamber, classically described as the "snow-globe" effect, representing inflammatory cells and purulent material.

5. THE SCORING MATRIX (Risk Stratification & Guidelines)

• ED Triage Algorithm: According to the diagnostic algorithm for red and painful eyes, the presence of severe pain and limbal injection strictly categorizes the patient out of the "Non-Urgent/Urgent" conjunctivitis pathways and into the "Emergent" pathway, mandating immediate workup.
• The Endophthalmitis Vitrectomy Study (EVS) Criteria : This is the gold-standard guideline used by ophthalmologists to dictate disposition and surgical intervention:
• Vision better than light perception (e.g., hand motion or counting fingers): Indicated for bedside vitreous tap and intravitreal antibiotic injection.
• Vision is light perception only: Indicated for emergent Pars Plana Vitrectomy (surgical washout) in the OR.

6. THE DANGER ZONE (Pitfalls & Critical Actions)

• The Endogenous Trap: Failing to recognize that a patient with endophthalmitis who is also febrile and tachycardic is actually suffering from systemic bacteremia (endogenous seeding). You must treat the systemic sepsis simultaneously, not just the eye.
• The "Conjunctivitis" Trap: Discharging a patient with a painful red eye who recently had cataract surgery or an intravitreal injection with topical antibiotic drops, mistaking early endophthalmitis for simple conjunctivitis.
• Critical Action: New acute vision loss combined with a red eye requires an emergent ophthalmology evaluation in the ED to prevent permanent blindness.

7. MCQ MASTERCLASS (Written Exam Tips)

• Buzzwords: "Recent cataract surgery," "recent macular degeneration injection," "blunting of the red reflex", "hazy intraocular media", "hypopyon."
• Distractor Options: An MCQ will present a patient with a painful red eye post-eye surgery. Distractors will include "Acute Angle-Closure Glaucoma" (incorrect, as IOP is usually normal to low in early endophthalmitis and the pupil is not fixed/dilated) and "Viral Conjunctivitis" (incorrect, as it does not cause severe internal hazy media or a hypopyon).
• Pathology Fact: If the board question features an IV drug user or a patient with a liver abscess who suddenly develops a painful, red, blind eye—the mechanism is endogenous hematogenous seeding.

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

"I am evaluating a patient presenting with an acute, painful, red eye and significant vision loss. My primary survey reveals hemodynamically stable vitals, making an endogenous bacteremic source less likely, though I will continue to monitor for systemic signs of sepsis. The history is highly concerning for exogenous endophthalmitis given the patient's recent cataract surgery. On my physical exam, visual acuity is severely diminished to hand-motion only. I note diffuse conjunctival injection, hazy intraocular media, and a clearly blunted red reflex. My critical actions include keeping the patient NPO, elevating the head of the bed, administering IV antiemetics to prevent spikes in intraocular pressure, and placing a STAT urgent consult to Ophthalmology in the ED for an emergent vitreous tap and intravitreal antibiotic injection."