Effectiveness of Bifidobacterium bifidum BB00 as adjunctive therapy for postoperative dry eye: a double-blind, randomised, placebo-controlled trial

This study investigated the effect of Bifidobacterium bifidum BB00 supplementation on the prevention of postoperative dry eye (DE) following refractive surgery. In this randomised, double-blind, placebo-controlled trial, 100 patients received either BB00 (2 × 10 9 CFU/day) or placebo for 30 days. DE incidence, ocular surface disease index (OSDI), fluorescein breakup time (FBUT), and Schirmer I test results were assessed, while gut microbiota composition was analysed via 16S rRNA sequencing. Among the 89 participants who completed the study, BB00 supplementation significantly reduced DE incidence and improved OSDI, FBUT, and Schirmer I values (all p < 0.05) compared with placebo. Surgery-induced dysbiosis, characterised by reduced Bifidobacterium and elevated Prevotella abundance, was partially reversed. Although BB00 supplementation delayed DE onset and improved ocular surface parameters, no significant effect on corneal healing was observed under the experimental conditions applied ( p > 0.05). • First clinical evidence that perioperative ophthalmic interventions induce gut microbiota dysbiosis in patients. • Oral BB00 significantly reduced dry eye incidence and improved ocular surface metrics after laser refractive surgery. • BB00 supplementation reversed surgery-induced dysbiosis, increasing Bifidobacterium and reducing Prevotella colonization. • First clinical evidence demonstrating the efficacy and safety of probiotic for alleviating postoperative dry eye.