Acoustic transients following excimer laser ablation of the cornea

Pressure transients occurring inside the eyeball as a consequence of excimer laser ablation of the cornea were measured at various distances along the optical axis, on enucleated porcine eyes. Positive (compressive) pressure spikes up to 90 bars were observed, lasting 100 ns, and developing, as they propagated in the eyeball, satellite rarefaction pulses with negative pressure as high as -40 bar. Such rarefaction wavefronts can trigger the formation of cavitation bubbles, in both the anterior and posterior chamber, depending on the ablation geometry. The potential risks associated with these photoacoustic phenomena, particularly for retina and corneal endothelium, are outlined.