AbstractObjectiveThis retrospective study evaluates the efficacy of povidone‐iodine (PI) and polyhexamethylene biguanide (PHMB) as preoperative antiseptics in equine ophthalmic procedures.Animals StudiedHorses that underwent routine ophthalmic surgery and procedures.ProceduresData were collected retrospectively from the medical records of equine patients undergoing ophthalmic procedures. Inclusion criteria were sampling for aerobic microbial culture at three different time points (T0: pre‐irrigation, T1: post‐irrigation, and T2: postoperatively) and T0 showing bacterial growth. Microbiological outcomes were assessed semi‐quantitatively by creating a scoring system to describe the bacterial load. Furthermore, the species detected were evaluated. Poisson regression analysis was performed to evaluate the efficacy of the disinfectants.ResultsEighty eyes (75 horses) met the inclusion criteria, with 36 cases being aseptically prepared with PI and 44 with PHMB. Both antiseptics significantly reduced the bacterial load and number of bacterial species (p < .001) between time points T0 and T1, and T0 and T2. PHMB showed a reduction in the bacterial load by 64% (CI: 51%–73%) whereas PI reduced it by 48% (CI: 36%–58%) between time points T0 and T1. The reduction in the number of bacterial species between time points T0 to T1 was significantly greater in the PHMB group (85%, CI: 70%–93%), compared to PI (47%, CI: 26%–62%).ConclusionBoth PHMB and PI reduced the bacterial load and number of species on the ocular surface and eyelids significantly, with 0.1% PHMB being superior to 0.2% PI. Therefore, PHMB can be considered as a good alternative in preoperative antisepsis in equine ophthalmic procedures.