Regional anesthesia in orbit can reduce ocular blood flow, increase in intraocular pressure (IOP) or the pharmacological action of local anesthetics. This study was conduced to evaluate the effects of clonidine added to lidocaine in IOP, ocular perfusion pressure (PPO) and ocular pulse amplitude (OPA) in patients undergoing cataract surgery under sub-Tenon's and peribulbar anesthesia.