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Purpose: To evaluate the microbial etiology and associated risk factors among patients with blebitis following trabeculectomy., Materials and Methods: A retrospective analysis of all culture-proven blebitis was performed in patients who underwent trabeculectomy between January 2004 and December 2008. A standardized form was filled out for each patient, documenting sociodemographic features and information pertaining to risk factors. Swabbing of the infected bleb surface was performed for all suspected cases and further subjected to microbiological analysis., Results: A total of 23 patients with culture-proven blebitis were treated during the study period, with a mean age of 59.2 years (59.2 ± SD: 12.8; range, 30-81 years). Duration of onset was early (≤ 36 months) in six (26%) cases and late (> 36 months) in 17 (74%) cases with a range between 15 and 144 months (mean, 82.91 months; SD: 41.89). All 23 blebs were located superiorly and of which, 21 (91%) were microcystic avascular, 1 (4%) diffuse avascular, and 1 (4%) vascular flattened. The predominant risk factor identified was bleb leak (35%; 8 of 23) followed by thin bleb (22%; 5 of 23) and blepharitis (17%; 4 of 23). Bleb leaks (100%) were recorded only in patients with late onset (≥ 9 years) of infection (P< 0.001), while the incidence of ocular surface disease (100%) occurred early (≤ 3 years) (P< 0.001). Use of topical steroids was associated frequently with cases of thin blebs (80%; 4 of 5) (P< 0.001), while topical antibiotics showed bleb leaks (88%; 7 of 8) (P< 0.001). Coagulase-positive staphylococci were frequently recovered from blebitis with thin blebs (71%; 5 of 7) (P = 0.001), Coagulase-negative staphylococci (CoNS) with bleb leak (100%; 8 of 8) (P< 0.001), Corynebacterium with blepharitis (100%; 3 of 3) (P = 0.001), and Streptococci with releasable sutures (75%; 3 of 4) (P = 0.001)., Conclusion: Bleb leak is the principal risk factor responsible for late-onset blebitis, while early-onset blebitis could be ascribed to ocular surface diseases. Streptococci were mainly responsible for early onset of infection, while the late onset was due to CoNS.