Epidemiology & Risk Factors

Exogenous (most common):
- Postoperative ocular surgery: Cataract extraction (most common trigger, typically within 1–2 weeks post-op).
- Trauma: Penetrating ocular injury, retained intraocular foreign body.
- Intravitreal injections (e.g., anti-VEGF for AMD).
Endogenous:
- Hematogenous spread from distant focus (e.g., infective endocarditis, indwelling CVC, IVDU).
- Immunocompromised status, prolonged TPN.
Common Pathogens:
- Coagulase-negative Staphylococci (e.g., S. epidermidis — most common post-op).
- Staphylococcus aureus, Streptococcus spp.
- Gram-negative bacilli (e.g., Pseudomonas aeruginosa).
- Candida albicans (most common endogenous agent, especially in IVDU/TPN).

Clinical Features

Symptoms:
- Rapidly progressive visual loss / decreased visual acuity (VA).
- Significant ocular pain and photophobia (can be mild in indolent coag-negative Staph).
- Redness, floaters, eyelid swelling.
Physical Exam:
- Hypopyon (layering of WBCs in anterior chamber).
- Vitritis: Vitreous haziness, loss of red reflex, obscured fundus visualization.
- Conjunctival injection and chemosis.
- Corneal edema, ciliary flush.
- Endogenous Candida: Funduscopic exam reveals focal white, fluffy, chorioretinal lesions extending into the vitreous (“string-of-pearls” appearance).

Initial / Clinical:
- Urgent slit-lamp biomicroscopy & dilated fundus exam demonstrating anterior chamber reaction and vitreous exudates.
Confirmatory / Gold Standard:
- Vitreous tap / biopsy (or anterior chamber paracentesis): Gram stain, bacterial/fungal cultures, and PCR.
Key Labs:
- Blood cultures (mandatory if endogenous source suspected).
- Fungal biomarkers (e.g., 1,3-β-D-glucan) if endogenous fungemia suspected.
Imaging:
- B-scan ocular ultrasound: Indicated when dense vitritis/corneal edema precludes direct fundus visualization (evaluates vitreous debris, choroidal thickening, retinal detachment).

Toxic Anterior Segment Syndrome (TASS):
- Diff: Sterile post-op inflammatory reaction presenting within 12–24 hours (vs. days to weeks in endophthalmitis); vitreous is clear; responds rapidly to topical steroids.
Acute Anterior Uveitis (Iritis):
- Diff: Leukocytes confined to anterior chamber; normal red reflex and clear vitreous; no history of intraocular surgery/trauma.
Acute Angle-Closure Glaucoma:
- Diff: Markedly elevated IOP (>40–50 mmHg), fixed mid-dilated pupil, “steamy” cornea, headache/nausea; absent hypopyon/vitritis.
Bacterial Keratitis (Corneal Ulcer):
- Diff: Infection limited to corneal stroma with overlying epithelial defect visible on fluorescein staining; intraocular vitreous initially uninvolved.
Orbital Cellulitis:
- Diff: Extraocular muscle restriction, painful ophthalmoplegia, proptosis; internal eye structures (vitreous/retina) are clear.

Immediate Step:
- Emergent Ophthalmology consultation (vision-threatening emergency).
First-line Medical Therapy:
- Intravitreal empiric broad-spectrum antibiotics:
  - Vancomycin (Gram-positive coverage) + Ceftazidime or Amikacin (Gram-negative coverage).
- If fungal etiology suspected/confirmed:
  - Intravitreal Amphotericin B or Voriconazole + systemic antifungals (e.g., IV/PO Voriconazole or Fluconazole).
- Adjunctive therapy: Topical cycloplegics (for ciliary spasm/pain) and delayed topical corticosteroids (to reduce inflammatory damage after Abx initiated).
Procedural / Refractory:
- Pars Plana Vitrectomy (PPV):
  - Indicated immediately for patients with profound vision loss (light perception only or worse, per EVS guidelines).
  - Indicated for retained intraocular foreign body, fungal endophthalmitis, or clinical deterioration despite intravitreal Abx.

Permanent vision loss / blindness.
Retinal detachment.
Panophthalmitis (extension beyond intraocular space to entire eyeball/orbit).
Phthisis bulbi (atrophic, non-functioning, shrunken eye).
Enucleation or evisceration.

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