Optimization of Orbital Retraction During Endoscopic Transorbital Approach: Quantitative Measurement of Intraocular Pressure - SevEN 006

Background: Increased utilization of transorbital approach (TOA) necessitates study of the risk of increased intraocular pressure (IOP) and intraorbital pressure (IORP) due to orbital compression. We aimed to investigate the changes in IOP and IORP in response to orbital retraction in TOA and establish a method for continuous measurement of intraoperative IORP.Methods: We investigated nine patients who underwent TOA surgery from January 2017 to December 2019, and five cadavers. IORP and IOP were measured using a cannula needle monitor, tonometer, cuff manometer, and micro strain gauge monitor.Results: In all nine clinical cases and five cadavers, increased physical compression of the orbit increased the IOP and IORP in curvilinear pattern. In clinical cases, when the orbit was compressed 1.5 cm from the lateral margin in the sagittal plane, mean IOP and IORP levels were measured at 25.4±5.2 mmHg and 14±9.2 mmH2O, respectively. The IORP reflected the IOP satisfactorily (Pearson correlation coefficient=0.824, p<0.001).Conclusion: We measured IOP and IORP simultaneously during orbital compression offering the basic information of the pressure change. In clinical cases, we found that the change in IOP can be monitored conveniently and noninvasively using continuous IORP measurement.