ObjectiveTo investigate the clinical settings, antibiotic susceptibilities, management and outcomes of streptococcal endophthalmitis. MethodsA retrospective observational case series study. Fifty six eyes of 56 patients diagnosed with streptococcal endophthalmitis in Eye & ENT Hospital, Fudan University from 2012 to 2022 were collected. The treatment followed the general principles of relevant guidelines, including pars plana vitrectomy (PPV), vitreous injection of antibiotics (IVI), vitreous injection of glucocorticoids and systemic application of antibiotics. The follow-up time was (11.9±17.0) months. Patients' clinical characteristics, pathogenic distribution and antibiotic susceptibilities, treatment and outcomes in their medical records were retrospectively collected and analyzed. ResultsAll 56 patients had monocular onset, including 39 (69.6%, 39/56) males and 17 (30.4%, 17/56) females, 26 (46.4%, 26/56) with left eyes involved and 30 (53.6%, 30/56) with right eyes involved. Their average age was (25.0±24.4) years. Ocular trauma was the leading cause of streptococcal endophthalmitis (73.2%, 41/56), followed by ophthalmic surgery (23.2%, 13/56) and endogenous infection (3.6%, 2/56). The streptococcal species included Streptococcus viridans (50.0%, 28/56), Streptococcus pneumoniae (18/56, 32.1%) and β-hemolytic Streptococcus (17.9%, 10/56). The susceptibility rates of Streptococcus to penicillin, cefatriaxone, vancomycin and levofloxacin were 66.0%, 57.1%, 94.1% and 92.4%, respectively. Patients received PPV+IVI and IVI as initial treatment were 49 eyes (87.5%, 49/56) and 7 eyes (12.5%, 7/56), respectively. Vitreous injection of glucocorticoids were performed in 17 eyes (30.4%, 17/56); and systemic antibiotics were applied in 52 cases (92.9%, 52/56). At the final follow-up, 47 eyes were recorded with visual acuity. Twenty (35.7%, 20/56) had best corrected visual acuity (BCVA)≥0.05 and 27 (48.2%, 27/56) had BCVA ＜0.05, of which 1 (1.8%, 1/56) had an eyeball enucleation. The etiology of endophthalmitis, streptococcal species, initial treatment with PPV, vitreous injection of glucocorticoids, and systemic antibiotics did not significantly affect patients' visual outcomes (P＞0.05). Timely visit to the hospital after the onset of symptoms (≤3 days) was significantly associated with achieving a final BCVA above 0.05 (P=0.025). ConclusionsOcular trauma was the primary cause of streptococcal endophthalmitis. Streptococcus viridans is the most common pathogenic bacterium. Streptococci had high susceptibility to vancomycin, but patients' visual outcomes were poor.