Objective To observe and analyze the risk factors of positive conjunctival capsule microbial culture in patients with intravitreal injection (IVT) before treatment. MethodsA prospective study. A total of 1 092 patients who received IVT at the Vitreous Injection Center of Tianjin Medical University Eye Hospital from February 2021 to February 2024 were included in the study. Among them, 539 were males and 553 were females. The age was (62.29±13.61) years. Hypertension and diabetes were 661 and 576 cases, respectively. There were 742 cases of urban residence and 350 cases of rural residence. Three and one days before IVT, 364 patients received antibiotics and 364 patients did not receive antibiotics. Patients' gender, age, history of hypertension and diabetes, pre-IVT antibiotic eye drops use history, and differences in residence (town/country) were collected in detail. Samples were collected after the conjunctival sac was rinsed, and microbial culture was performed. The differences in conjunctival microbial culture positivity rates was compared between those who did not use antibiotic eye drops before IVT, those who used them 1 day before IVT, and those who used them 3 days before IVT. The positive rate of conjunctival sac microbial culture were compared among individuals of different ages, genders, with/without hypertension, with/without diabetes, with different IVT times, and from different living areas (urban/rural). The clinical baseline of positive conjunctival capsule bacterial culture was compared and observed. χ2 test was used to compare the positive rate of conjunctival capsule microbial culture among different clinical baselines. Logistic binary regression analysis was used to analyze the influencing factors. ResultsAmong the 1 092 patients, 54 cases (4.95%, 54/1 092) were positive for microbial culture of conjunctival sac. There was no significant difference (P＞0.05) in the positive rate of conjunctival sac microbial culture among patients of different ages (χ2=5.599), gender (χ2=0.549), residence (χ2=0.153), with or without hypertension and diabetes (χ2=3.545, 0.044), and with or without diabetic macular edema (χ2=0.180). There was no significant difference (P＞0.05) in the positive rate of conjunctival sac microbial culture between patients with different numbers of IVT (χ2=0.961) or between those who received antibiotic eye drops before IVT and those who did not (χ2=5.600). Logistic binary regression analysis showed that none of the above factors were risk factors for positive conjunctival capsule microbial culture (P＞0.05). No infective endophthalmitis occurred in all patients during the observation period. ConclusionThe use of antibiotics before IVT is not the decisive factor for positive microbial culture in conjunctival sac.