Sub-Tenon's anesthesia is now widely regarded as a preferred local anesthetic method for cataract surgery. Various techniques have been explored to prolong the duration, shorten onset time and improve the efficacy of local anesthetic nerve blocks with varying degrees of success. Warming local anesthetic may speed up its onset and prolong its effect by lowering its pKa.The aim of this study is to evaluate the effect of warming bupivacaine on the characteristics of a sub-Tenon's block in patients undergoing cataract surgery. It is hypothesized that warming bupivacaine 0.5% to 37C will improve the characteristics of sub-Tenon's block. It will prolong the duration of sensory and motor block and accelerate the time onset time of sensory and motor block.