Prospective Evaluation of Ocular Anterior Segment Morphology Changes in the Steep Trendelenburg Position During...

Background/Objectives: Surgery performed in the steep Trendelenburg position is considered potentially detrimental to ocular structures. This study aimed to evaluate morphological changes in the anterior segment during robot-assisted laparoscopic prostatectomy (RALP). Methods: This was a single-center, prospective observational study involving 60 eyes of 30 consecutive patients undergoing RALP between May and November 2021. Anterior segment images were obtained using a Smart Eye Camera before surgery (supine and awake), during surgery (supine and steep Trendelenburg under anesthesia), and after surgery (supine). Assessed parameters included the iridocorneal angle, the ratio of peripheral anterior chamber depth to peripheral corneal thickness based on Van Herick Plus grading, and pupil diameter. Each parameter in the steep Trendelenburg position under anesthesia was compared with measurements obtained in the supine position under anesthesia and in the awake condition. The primary outcome was the comparison of anterior segment morphological changes between the supine and steep Trendelenburg positions during RALP. Results: Upon transition to the steep Trendelenburg position, anterior chamber depth significantly decreased (p < 0.001), recovering after returning to the supine position. The proportion of eyes classified as having narrowed anterior chambers increased significantly (p < 0.001), with more than 60% showing shallower chambers relative to preoperative measurements. Extreme anterior chamber narrowing occurred in 3 out of 410 intraoperative assessments (1%). Pupils were uniformly constricted under anesthesia. Conclusions: Steep Trendelenburg positioning significantly reduces anterior chamber depth. This morphological alteration may contribute to the marked increase in intraocular pressure observed during RALP.