Background
Elderly patients may present with visual function impairment after surgery, which may increase the incidence of postoperative delirium and falls and decrease their quality of life. The aim of this study was to assess visual function in elderly patients after long-duration nonocular surgery to determine the incidence and risk factors for visual function impairment after surgery.

Methods
This prospective and observational study included patients aged between 60 and 80 years who had been scheduled for elective non-ocular surgery expected to last longer than 120 minutes under general anaesthesia. Ocular examinations were performed before surgery, on post-operative day 3 and on post-operative day 21 and consisted of a LogMAR-Snellen chart test, a Jager chart test, biomicroscopy, optical tonometry, ocular motility assessment and fundoscopy. Baseline characteristics of all patients as well as intraoperative and postoperative data were collected.

Results
A total of 107 patients were included in the final analysis. Visual function impairment was diagnosed in 21 patients (19.6%) at POD 3. Of those, 7 patients (6.5%) still presented with visual changes at POD 21. On POD 3, compared with that at baseline, visual acuity assessed by the Snellen chart test had decreased in these patients. Significant differences regarding refraction tests and intraocular pressure measures were also found. Multivariable analysis identified diabetes mellitus, duration of surgery, hypotension during anaesthesia induction, lower peripheral oxygen saturation at the end of the procedure and body mass index as independent risk factors for postoperative visual impairment.

Conclusion
In elderly patients undergoing long-duration non-ocular procedures under general anaesthesia, the incidence of visual function impairment was considerably high. Most patients recovered to baseline visual function, but clinically significant visual changes may still be present 3 weeks after surgery. Obesity, diabetes mellitus, and the duration of surgical and anaesthetic techniques appear to increase the risk of visual impairment after surgery.