Improved surgical and anesthetic techniques have made off pump coronary artery bypass surgery feasible. During this procedure grafting of the left circumflex and posterior descending arteries often requires a steep Trendelenburg position which increases intraocular pressure. This rise in pressure can reduce ocular perfusion and may lead to ischemic optic neuropathy and postoperative visual loss. Although rare these complications can be severe and permanent. The reported incidence of visual loss in cardiac and spine surgeries ranges from very low to around 0.2 percent and is multifactorial. Data specific to off pump surgery is limited but some studies suggest a measurable risk.

Studies comparing on pump and off pump cardiac surgery show that intraocular pressure decreases during cardiopulmonary bypass but increases during off pump procedures especially in the Trendelenburg position. Various anesthetic agents have been studied to control this increase with inconsistent results and there is limited evidence in off pump cardiac surgery.

Increased episcleral venous pressure is one of the mechanisms for raised intraocular pressure. Alpha 2 agonists reduce intraocular pressure by decreasing aqueous production and increasing outflow. Dexmedetomidine is a highly selective alpha 2 agonist that provides sedation and hemodynamic stability and has shown cardioprotective effects in off pump surgery. Based on these properties this study aims to evaluate whether dexmedetomidine can reduce the rise in intraocular pressure during off pump coronary artery bypass surgery.