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

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.

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.

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 ( R 1 = 0.66, R 2 = 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.

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.