Purpose: We report a case of unilateral acute iris transillumination (AIT) and iris sphincter paralysis in a 63-year-old male undergone uneventful phacoemulsification surgery with intracameral moxifloxacin (ICM). Case presentation: This is a case of AIT with no history of viral disease or use of systemic fluoroquinolone but an association with ICM after uneventful phacoemulsification. The clinical features of the affected eye are perfectly similar to what has been described in BAIT and hence we consider that unilateral AIT and BAIT share the same etiopathogenesis. At the end of the phacoemulsification, the patient received 0.15 ml of 5mg/ml moxifloxacin, which is notably higher than the dose that is commonly used for ICM. This may have caused the patient to develop BAIT-like syndrome after the ICM. Conclusion: 0.1 ml of 5mg/ml moxifloxacin or less should be used to reduce the risk of occurrences of this toxic effect caused by ICM.