Change in Intraocular Pressure and Ocular Perfusion Pressure Due to Trendelenburg Positioning

This study increases foundational knowledge about the dynamic relationships between intraocular pressure (IOP), blood pressure (BP), and mean ocular perfusion pressure (MOPP) in the setting of steep Trendelenburg positioning and may inform medical decision making for patients in which this positioning is planned.

The purpose of this study was to explore the demographic and clinical factors related to IOP, MOPP, and BP change during Trendelenburg positioning in a large sample of subjects.

A single-cohort interventional study was conducted at the American Academy of Optometry 2017 annual meeting. Baseline demographic data were collected by a secure survey tool. IOP and BP were then measured while seated and again after 1 and 2 minutes in a steep Trendelenburg position. Raw and percentage differences for each variable were compared between time points, and regression analyses demonstrated factors related to change in IOP, BP, and MOPP during steep Trendelenburg positioning.

Median IOP increased from 16.3 mmHg (13.3 to 18.3 mmHg) at baseline to 25.0 mmHg (21.7 to 28.7 mmHg) at 1 minute after assuming the Trendelenburg position. More than 95% of individual eyes exhibited an IOP increase of at least 10%, and 45% had an IOP increase of 10 mmHg or greater. Correspondingly, MOPP fell from 50.3 mmHg (43.4 to 55.4 mmHg) at baseline to 36.3 mmHg (31.9 to 43.3 mmHg). Mean ocular perfusion pressure decreased by at least 10 in 90% of eyes. In multivariate regression analysis, factors independently related to percentage IOP increase were increasing weight, less myopic refractive error, lower baseline pulse, and lower baseline IOP (total r = 0.31, P < .001). Conversely, weight was the only variable independently related to percent MOPP change, and this relationship was weak (r = 0.05, P = .008).

Our results confirm that steep Trendelenburg positioning causes an increase in IOP and a decrease in MOPP in almost all eyes. Considering the identified causative factors will inform clinical education and provide foundational knowledge for future investigations.