 Postoperative cognitive disorder POCD and postoperative delirium POD are the most common complications of geriatric surgical patients, which could cause long-term social dysfunction, high mortality and increased medical cost. Currently, there is no biomarker for POCDPOD, and it also remains largely unknown whether different anesthesia might lead to different incidence and severity of POCDPOD. The investigators previous studies showed that thickness of retinal nerve fiber layer thickness RNFL-T measured by optical coherence tomography OCT was associated with POCDPOD; change of RNFL thickness RNFL-C in certain period correlated with cognitive deterioration converted to Alzheimers disease. Thus, the investigators consider that RNFL is a potential biomarker of POCDPOD. In the proposed large-scaled longitudinal studies, the investigators will clinically validate RNFL-T as pre-operative POCDPOD biomarker, and RNFL-C as post-operative biomarker of POCDPOD. Finally, the investigators will compare the effects of surgery total hipknee replacement under general anesthesia with sevoflurane and propofol on the incidence and severity of POCDPOD in patients. The hypothesis is that patients who have total hipknee replacement under propofol anesthesia will have less POCDPOD as compared to patients who have the surgery under sevoflurane anesthesia. Moreover, RNFL thichkenss is associated with incidence and severity of POCDPOD. Results from the proposed studies will likely establish RNFL as a potential POCDPOD biomarker, promote the clinical utilization of OCT-RNFL in early screening and outcome prediction of POCDPOD, and finally optimize anesthesia care of geriatric surgical patients to avoid or reduce POCDPOD incidence. These findings will improve the anesthesia care and lead to better postoperative outcomes of geriatric patients. 