Novel modeling of ultrasonic wave propagation in ophthalmic tissue

Abstract

Ultrasound has been widely used to diagnose a variety of anomalies present in ophthalmic tissue (detached retinas, tumors, cataracts, etc.), and to obtain a number of measurements in the eye like intraocular length, lens thickness, and so on. However, there has not been a clear understanding of how ultrasonic waves propagate and interact with the layers of the eye, and whether safety concerns are an issue. This presentation discusses two novel modeling techniques to complement these already existing tools to enhance ultrasonic evaluations of the eye by providing additional insight and a theoretical frame of reference. Axisymmetric finite element and PSpice transmission line models simulating a single-element transducer based on Redwood’s version of Mason’s equivalent circuit, a focusing lens, and a multi-layered medium that mimics propagation of ultrasound in the different layers of the eye are presented. Results are obtained for a normal eye and for one in the case of a retinal detachment. A-scans are also obtained in vitro using an extracted normal sheep’s eye for comparison. Both sets of results clearly show the transmission and reflection of the ultrasonic waves as they travel through the layers within the eye structure and confirm the validity of these modeling techniques.