Post-Cataract Surgery Endophthalmitis vs. Sterile Inflammation
A 68-year-old man with type 2 diabetes (HbA1c 8.9%) undergoes uncomplicated phacoemulsification with posterior chamber IOL in the right eye. On postoperative day 3, he presents with pain, decreased vision to counting fingers, and a red eye. Examination shows a hypopyon of 2 mm, diffuse corneal edema, and no view of the fundus. Intraocular pressure is 8 mmHg. He was started on topical prednisolone acetate 1% and moxifloxacin four times daily after surgery. He reports poor compliance with drops. A vitreous tap is performed, and Gram stain shows gram-positive cocci in clusters.
1. Distinguish the most likely infectious organism and explain how the timing and clinical findings support your diagnosis over sterile postoperative inflammation.
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Most likely organism: Coagulase-negative Staphylococcus (gram-positive cocci in clusters), the commonest cause of acute post-cataract endophthalmitis.
Timing: Presentation at day 3 fits acute bacterial endophthalmitis (typically 3–7 days), whereas sterile inflammation (e.g., toxic anterior segment syndrome) usually presents within 12–48 hours and is not associated with pain or a positive Gram stain.
Supporting findings:
- Pain and marked vision loss (CF) are red flags for infection.
- Hypopyon and diffuse corneal edema reflect intense anterior segment inflammation.
- Low IOP (8 mmHg) suggests ciliary body shutdown from severe inflammation.
- Gram-positive cocci confirm bacterial infection; sterile inflammation would have a negative Gram stain.
Against sterile inflammation: TASS typically has a clear cornea, no pain, and a limbus-to-limbus uniform haze; it responds to steroids and does not yield organisms on tap.
2. Outline your immediate management plan, including the rationale for intravitreal antibiotics versus systemic antibiotics, and the role of vitrectomy.
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Immediate management:
- Intravitreal antibiotics - vancomycin 1 mg/0.1 mL plus ceftazidime 2.25 mg/0.1 mL (covers gram-positive and gram-negative organisms). This is the standard of care because the blood–retinal barrier limits systemic drug penetration into the vitreous.
- Vitreous tap for Gram stain, culture, and sensitivity before antibiotics (already done).
- Topical fortified antibiotics and steroids as adjuncts.
- Systemic antibiotics are not routinely recommended; they add little to intravitreal therapy and are reserved for specific situations (e.g., severe infection, systemic spread).
Role of vitrectomy:
- Immediate vitrectomy is indicated if vision is light perception only, or if there is severe vitreous involvement. It debulks infected vitreous, removes inflammatory mediators, and improves antibiotic distribution.
- In this patient with CF vision, a tap and inject may suffice, but if vision deteriorates to light perception or fails to improve, vitrectomy should be performed.
Follow-up: Reassess within 24–48 hours; repeat tap and inject if no improvement.