Endophthalmitis is severe intraocular inflammation involving the vitreous humor, anterior chamber, and surrounding intraocular tissues. The condition is most commonly bacterial (90%), with fungal etiology in chronic and post-traumatic cases. Endophthalmitis is classified by etiology and timing: acute postoperative (within 6 weeks of surgery, typically with virulent pathogens), delayed/chronic postoperative (>6 weeks, indolent organisms like P. acnes), bleb-associated (post-trabeculectomy, often Streptococcus), post-traumatic (especially with retained intraocular foreign body), endogenous (hematogenous spread from systemic infection, more often fungal), and post-intravitreal injection (increasingly recognized with anti-VEGF therapy expansion). Each category has distinct organisms, presentations, prognoses, and management strategies.
The most common pathogens vary by category. Acute postoperative endophthalmitis: coagulase-negative Staphylococcus (most common, 70%), S. aureus, Streptococcus species, Enterococcus, gram-negative rods. Delayed postoperative: P. acnes, S. epidermidis, fungi. Bleb-associated: Streptococcus, gram-negative rods (poor prognosis). Post-traumatic: Bacillus species (rapidly destructive), gram-positives, fungi. Endogenous: bacterial (S. aureus, gram-negatives, especially in IV drug users) or fungal (Candida species, especially albicans). Post-injection: similar to postoperative. Risk factors include diabetes mellitus, immunosuppression, posterior capsule rupture during cataract surgery, vitreous loss, retained intraocular foreign body, blepharitis, and proximity of injection to eyelid.
Clinical presentation typically includes severe ocular pain, decreased vision (often profound), conjunctival injection, hypopyon (layered white blood cells in anterior chamber), corneal edema, vitreous inflammation, and absent red reflex. Symptoms develop hours to days post-procedure or following predisposing event. Diagnosis is primarily clinical with confirmatory aqueous and vitreous samples obtained at the time of treatment. The Endophthalmitis Vitrectomy Study (EVS, 1995) established management guidelines: all cases should receive immediate vitreous tap (preferable over aqueous as higher pathogen yield) for culture and intravitreal antibiotic injection (vancomycin 1 mg/0.1 mL covers gram-positives plus ceftazidime 2.25 mg/0.1 mL for gram-negatives, or amikacin 0.4 mg/0.1 mL alternative). Pars plana vitrectomy is indicated for vision worse than light perception per EVS, though many specialists now perform vitrectomy more liberally. Adjunctive intravitreal dexamethasone (400 μg) may reduce inflammation. Topical fortified antibiotics, oral antibiotics with vitreous penetration (moxifloxacin, ciprofloxacin), and close follow-up are standard. Despite treatment, visual outcomes are poor: 50% achieve 20/40 or better, but 25% have <20/200 final vision. Prevention through preoperative povidone-iodine, perioperative antibiotics, and aseptic technique is critical.