Microbiologic factors and visual outcome in the endophthalmitis vitrectomy study

PURPOSE: To evaluate the relationship between microbiologic factors, effect of treatment, and visual outcome in the Endophthalmitis Vitrectomy Study. METHODS: Four hundred twenty patients were enrolled in the Endophthalmitis Vitrectomy Study between February 1990 and January 1994. Of these, 394 completed 9 to 12 months of follow-up. Patients presented with features of bacterial endophthalmitis within 6 weeks of cataract extraction or secondary intraocular lens implantation. The relations between visual outcome and the identity of infecting species, gram stain results, antibiotic susceptibilities, and presence of vitrectomy cassette growth were examined. RESULTS: Rates of achieving final visual acuity of 20/100 or better for the more common isolates were as follows: gram-positive, coagulase-negative micrococci, 84%; Staphylococcus aureus, 50%; streptococci, 30%; enterococci, 14%; and gram-negative organisms, 56%. A positive gram stain or infection with species other than gram-positive, coagulase-negative micrococci were significantly associated with poorer visual outcome (P <.001 for species group comparisons). However, presenting visual acuity was more powerful than microbiologic factors in predicting visual outcome and favorable response to vitrectomy. Bacterial growth from the vitrectomy cassette specimen had prognostic significance equivalent to growth from other intraocular sources. CONCLUSIONS: Visual prognosis was strongly associated with the type of infecting organism and gram stain positivity. However, visual acuity at initial presentation appeared to be more useful than microbiologic factors in predicting visual outcome and judging the value of immediate vitrectomy in acute bacterial endophthalmitis after cataract surgery.