The rate of postoperative delirium in patients who underwent cardiac surgery is very high. Different predictors and/or scores were studied for the prediction of Post Operative Delirium (POD)after heart surgery, but none of them was validated. The investigators aim to explore the role of pupillary alterations during anesthesia in open-heart surgery. The goal of this prospective study is to evaluate if pupil alterations during cardiac surgery, evaluated by an automated pupillometer (NPi-200) ( AP), could predict postoperative delirium.