The effect of the lateral decubitus position on the intraocular pressure in anesthetized patients undergoing lung surgery

Background: Changing the body position alters the intraocular pressure (IOP). The aim of this study was to investigate the alteration in IOP of the eyes after a positional change from a supine position to a lateral decubitus position in anesthetized patients, in order to detect differences in IOP between the two eyes, possibly due to a gravity effect, in the lateral decubitus position. Methods: IOP was measured in 20 patients undergoing lung surgery. IOP in both eyes was recorded prior to anesthesia in the supine position (baseline), after anesthetic induction but before tracheal intubation in the supine position, at the end of central venous catheterization in the Trendelenburg position, 5 min after a positional change to the lateral decubitus position, once every 30 min until the end of surgery in the lateral decubitus position, and 5 min after changing back to the supine position. Results: The median IOP (16.3 mmHg; 25-75% percentile, 13-20 mmHg) in the dependent eye 5 min after changing to the lateral decubitus position increased significantly from the baseline median IOP (14.3 mmHg; 13-17.3 mmHg; P < 0.05). The increase in median IOP in the dependent eye persisted until the end of surgery in the lateral decubitus position (19 mmHg; 16.5-22.3 mmHg; P < 0.01 vs. baseline). The median IOP in the dependent eye was significantly higher than that in the non-dependent eye when anesthetized patients were placed in the lateral decubitus position (P < 0.01), and the mean differences in IOP between the eyes in the lateral decubitus position ranged from 2.9 to 4.1 mmHg. Conclusion: The IOP was higher in the dependent eye than in the non-dependent eye in anesthetized patients in the lateral decubitus position, and the IOP in the dependent eye increased in anesthetized patients compared with that in awakened and supine-positioned patients.