Generation of acoustic waves in the eye via cavitation during photoablation of corneal tissue

Abstract

During LASIK and other refractive correction surgeries, the shape of the cornea is modified by removal of tissue with high energy laser pulses. The laser beam deposits enough energy over a small spot size (approximately 1 mm diameter) to create a cavitation event from localized heating. Multiple pulses are delivered at different locations on the cornea to remove tissue selectively and reshape its surface in effort to minimize optical wavefront aberrations. Cavitation with each pulse can generate an acoustic wave that propagates within the eye and potentially damage sensory cells in the retina. A mathematical model was created to investigate this phenomenon and understand the effects of laser spot size and pulse repetition frequency on characteristics of the acoustic wave. Motion associated with the cavitation event was treated as a point source on the surface of a spherically shaped eye globe. A spatial map of internal acoustic pressure amplitudes was then created; results indicate that operational parameters can be adjusted to help prevent deleritous effects of cavitation-induced stress waves on the retina during refractive correction surgery.