Impact of microorganism virulence on endophthalmitis outcomes

Aims: To determine the impact of microorganism virulence on visual outcomes in endophthalmitis.

Methods: Retrospective, multicentre cohort study of patients presenting with endophthalmitis between 2006 and 2021. A literature review was conducted to divide cultured microorganisms into low and high virulence subcategories.

Results: 610 eyes with endophthalmitis were recruited from New Zealand, the UK and Israel. The median age was 69.4 years. The median visual acuity was hand movements at presentation and 20/120 at the final follow-up. Severe visual loss (≤20/200) occurred in 237 eyes (38.9%) at the final follow-up. The culture-positive rate was 48.5% (296 eyes). Highly virulent microorganisms were associated with a 4.48 OR of severe visual loss at the final follow-up (p<0.001) and a 1.90 OR of developing retinal detachment or requiring enucleation or evisceration during the follow-up period (p=0.028). Oral flora were observed in 76 eyes (25.7%), and highly virulent microorganisms were observed in 68 eyes (22.9%). Highly virulent microorganisms were more likely to be found after glaucoma surgery (15 eyes, 34.9%) and vitrectomy (five eyes, 35.7%) compared with intravitreal injections (two eyes, 2.9%) and cataract surgery (22 eyes, 24.2%). On multivariate analysis, the following were associated with poorer visual outcomes: poor presenting vision (p<0.001), glaucoma surgery (p=0.050), trauma (p<0.001), oral microorganism (p=0.001) and highly virulent microorganism (p<0.001).

Conclusion: This is the first classification of microorganisms into high and low virulence subcategories that demonstrate highly virulent microorganisms were associated with poor visual outcomes and increased likelihood of retinal detachment and enucleation.