Assessing Porcine Iris Elasticity and Mechanical Anisotropy with Optical Coherence Elastography

The relaxation and contraction of the sphincter and dilator muscles of the iris play a critical role in vision, yet little is known about the biomechanical properties of these muscles. This study aimed to determine the elastic properties of the iris as a function of its anatomy and intraocular pressure. A high-resolution phase-sensitive OCE system was employed to detect acoustic radiation force induced propagation of elastic waves in the porcine iris in situ. Experiments were conducted at four different intraocular pressures (5, 10, 20, and 30 mmHg) with mechanical excitation at 1 kHz. We found that there was no significant difference in the wave speed at the different intraocular pressures. The results show that the stiffness of the iris was significantly higher in the semi-azimuthal orientation (mean wave speed of 2.5 m/s) than in the radial orientation (mean wave speed of 1.5 m/s). These measurements provide essential insights into the elastic properties of the iris, and they can be used for the characterization of eye conditions.