Characterizing regional biomechanical properties of the porcine iris using optical coherence elastography

Abstract

The fundamental physiological function of the iris is to control the amount of light entering the eye, which requires the coordinated constriction or dilation of the pupil, affected by two antagonistic muscles, namely the sphincter and radial muscles. Disorders of the iris, including these muscles, may lead to ocular pathologies, such as primary angle-closure glaucoma. Here, we assessed the regional biomechanical properties of the iris using phase-sensitive optical coherence elastography (PhS-OCE) to quantify the shear wave speed arising from perturbations generated using an acoustic radiation force (ARF) transducer of resonant frequency 3.5 MHz and focal length 19 mm. We determined regional shear wave speeds by tracking elastic wave propagation in ex vivo porcine irides. Results showed that the mean shear wave speed in the pupillary zone (~2.1 m/s) was consistently greater than in the ciliary zone (~1.87 m/s). These findings indicate that the mechanical properties of the iris exhibit regional heterogeneity, which may be related to the microstructure of the iris (muscle locations/extent) and intrinsic elastic properties.