Can antibiotic eye ointment change the natural bacteria living on your horse’s eye? New research suggests that topical antibiotics—with or without corticosteroids—can temporarily alter the equine ocular microbiota. These changes may remain after treatment ends, with the eye’s microbial community taking approximately three weeks to return close to its original composition.In this video, we explain what the equine ocular microbiota is, how researchers studied the effects of antibiotic eye ointments in healthy horses, and what the findings mean for horse owners. We also discuss why the untreated eyes changed during the study, the research limitations, and why these results do not mean that prescribed eye medications are unsafe.Horse eye problems can become serious very quickly. Squinting, excessive tearing, swelling, redness, discharge, cloudiness, or sensitivity to light can be signs of an ulcer, injury, infection, inflammation, or foreign material. Because several eye conditions can look similar, owners should never use leftover antibiotic or steroid-containing eye medication without first contacting a veterinarian.Corticosteroid eye medication can be appropriate for certain diagnosed conditions, but it may delay corneal healing or worsen some ulcers and infections. Always have your horse’s eye examined and follow your veterinarian’s treatment instructions.This video is for educational purposes only and is not a substitute for veterinary diagnosis or treatment.Chapters