Rho-associated protein kinase (ROCK) is one of the major downstream effectors of Rho GTPases, and the inhibition of ROCK lowers IOP of rats, rabbits, monkeys, and human patients with primary open-angle glaucoma.1, , –4 Exoenzyme C3 transferase (C3) is isolated from Clostridium botulinum and specifically inactivates Rho by ADP-ribosylation.5 We hypothesized that C3 has effects on aqueous outflow and IOP similar to ROCK inhibitors. Here, RHO is linked to glaucoma.