The Repeatability and Reproducibility of a New Minimally Invasive Method for Orbital Pressure Measurement

Background: Evaluation of orbital pressure is crucial for monitoring various orbital disorders. However, there is currently no reliable technique to accurately measure direct orbital pressure (DOP). This study aimed to establish a new method for the DOP as well as to verify its repeatability and reproducibility in rabbits.Methods: The study included 30 normal eyes from fifteen 3-month-old New Zealand white rabbits. After administering inhalation anesthesia, intraocular pressure (IOP) was determined by tonometry (Tonopen). For DOP manometry, a TSD104 pressure transducer was inserted between the disposable injection needle and the syringe, and the output results were displayed on a computer. Two observers independently participated in the experiment to verify its repeatability and reproducibility.Results: The mean IOP of rabbits was significantly higher than the DOP in normal rabbits (11.67 +/- 1.08 mm Hg versus 4.91 +/- 0.86 mm Hg, P < 0.001). No significant interocular difference was detected for both IOP and DOP (P > 0.05). A high correlation was found for intraobserver measurements of both IOP (intraclass correlation coefficient = 0.87, P < 0.001) and DOP (intraclass correlation coefficient = 0.89, P < 0.001). A high agreement was also presented for the interobserver reproducibility for the measurements of IOP [Pearson correlation coefficient (R) = 0.86, P < 0.001] and DOP (R = 0.87, P < 0.001). Direct orbital pressure was positively correlated with IOP in both observers (R1 = 0.66, R2 = 0.62, P < 0.001). The Bland-Altman plots revealed that 5.0% (3/60) of the IOP and DOP measurement points were outside of the 95% limits of agreement, respectively.Conclusions: The TSD104 pressure transducer-based manometry may serve as a reliable device for the measurement of DOP, providing real-time measuring results with acceptable reproducibility and repeatability.