Oxidative stress is one of the most important risk factors for cataractogenesis. Previous studies have indicated that BDS-II, a Kv3 channel blocker, plays pivotal roles in oxidative stress-related diseases. This study demonstrates that BDS-II exerts a protective effect on cataractogenesis. Specifically, BDS-II was observed to inhibit lens opacity induced by H 2 O 2. BDS-II was also determined to inhibit cataract progression in a sodium selenite-induced in vivo cataract model by inhibiting reduction of the total GSH. In addition, BDS-II was demonstrated to protect human lens epithelial cells against H 2 O 2 -induced cell death. Our results suggest that BDS-II is a potential pharmacological candidate in cataract therapy. • BDS-II treatment significantly inhibited the ex vivo and in vivo cataract progression induced by oxidative stress. • Rat lens and human lens epithelial cells were determined to express 4 different Kv3 subtypes, which are targets of BDS-II. • BDS-II protected human lens epithelial cells against oxidative stress-induced cell death. [ABSTRACT FROM AUTHOR]