Correlation of IOP with Corneal Acoustic Impedance in Porcine Eye Model

PURPOSE The aim of this study is to correlate the intraocular pressure (IOP) change with the acoustic impedance of the cornea, in order to propose a noncontact and noninvasive method for IOP monitoring. METHODS AND MATERIALS A highly focused transducer (frequency 47-MHz; bandwidth 62%) was made to measure the echo from the anterior and posterior surfaces of intact porcine eyes, respectively. A multilayered transmission and reflection model was used to calculate the acoustic impedance. The linear relationship between acoustic impedance and intraocular pressure was analyzed by statistical method. RESULT During pressure elevation from 10 mm Hg to 50 mm Hg, the mean acoustic impedance of the posterior cornea increased from 1.5393 to 1.5698 MRayl, which showed a strong linear correlation (R = 0.9849; P = 0.0022). Meanwhile, the mean value of the anterior cornea increased from 1.5399 to 1.5519 MRayl, and a less significant correlation was observed (R = 0.7378; P = 0.0025). CONCLUSION This study revealed a linear correlation between intraocular pressure and acoustic impedance of the cornea, thus demonstrating a potentially important method to noninvasively measure the intraocular pressure in vivo.