Epidemiology, Microbiology, Management and Outcomes of Endophthalmitis: An 18 Year Retrospective Observational Study at a Tertiary Referral Center in Australia

Purpose: This study characterizes the epidemiology, microbiological profile, management and outcomes of endophthalmitis over 18 years at a tertiary referral center in regional New South Wales (NSW), Australia. Methods: A retrospective observational study of all endophthalmitis cases at John Hunter Hospital (November 2006 to December 2024) identified via ICD-10 codes and confirmed via record review. Data included demographics, clinical presentation, etiology, microbiology, management and surgical interventions. Results: In total, 232 cases (227 patients) were identified (median age 75.6 years). Annual incidence declined significantly (slope = − 0.17 cases/year, 95% CI − 0.29 to − 0.052); p = 0.005). Exogenous endophthalmitis accounted for 87.1% of cases, most commonly following cataract surgery or intravitreal injection (38.1% each). Endogenous cases (12.9%) were mainly associated with bacteremia (56.7%) and immunosuppression (20%). Culture positivity was 56%, with 97.7% of isolates being bacterial. Gram positive cocci were identified in 84% of culture-proven cases, predominantly coagulase-negative staphylococci (42%), while gram-negative organisms comprised 9.4%. Intravitreal antibiotics were administered in 97.3% of cases and pars plana vitrectomy (PPV) performed in 41.5%. Overall, 52.5% of eyes improved in visual acuity. The Win Ratio for improvement with vitrectomy versus antibiotics alone was 1.31 in favor of vitrectomy (95% CI 0.77– 2.22; p = 0.31). In eyes presenting with light perception vision, the Win Ratio was 2.28 in favor of vitrectomy (95% CI 0.79– 6.55; p = 0.13). Conclusion: Exogenous endophthalmitis remains the leading cause of endophthalmitis at a major regional tertiary referral center. Findings align with the Endophthalmitis Vitrectomy Study, suggesting vitrectomy benefits mainly eyes presenting with light perception only vision. Plain Language Summary: What is Already Known on this Topic Endophthalmitis is a rare but serious infection inside the eye that can occur after surgery, intravitreal injections, trauma, or from infections elsewhere in the body. Although uncommon, it can cause permanent vision loss if not treated quickly. Earlier research shows that the causes and bacteria involved can change over time, particularly with the rapid growth of intravitreal injections. However, long-term Australian data, especially from regional centres, are limited. What This Study Adds This study presents an 18-year review of all endophthalmitis cases managed at a major regional hospital in New South Wales, Australia. It describes trends in how often cases occurred, the reasons they developed, the types of bacteria involved, and how patients were treated. It also compares visual outcomes between patients treated with intravitreal antibiotics alone and those who underwent vitrectomy surgery, and identifies which patients are most likely to benefit from surgery. How this Study Might Affect Research, Practice, or Policy The findings help clinicians recognise risk factors for poor outcomes and support decision-making around vitrectomy in severe cases. They also reinforce the importance of infection-prevention strategies in cataract surgery and intravitreal injections. Keywords: endophthalmitis, intravitreal injection, cataract surgery