Observation of microwave-induced eye lens surface motion in vitro

Previous experiments have shown that murine ocular lenses immersed in saline in vitro suffered microscopic physical damage (including cataractogenic changes) after exposure to pulsed microwaves under conditions in which the temperature rise was negligible. The suspected coupling mechanism is thermoelastic transduction (TET). To test this hypothesis, laser interferometry was used to measure the lens surface motion induced by pulsed microwaves. Although experimental constraints delayed the recording of surface motion data until 0.5 ms after the microwave pulse, damped oscillatory motion was measured over an interval of several milliseconds. A theoretical model is presented to explain the observed motion as natural oscillation modes of an elastic sphere excited by TET waves produced in the surrounding saline. Effects of the lens capsule are also discussed. The conclusions reached are that the observed motion is TET induced, but the lens damage occurs during the passage of the initial excitatory TET waves through the lens, an event which could not be monitored by this experiment.