Stress wave amplitudes during laser surgery of the cornea

Purpose: To determine the stress wave amplitudes generated during photoabla tion of the cornea using an argon fluoride excimer laser. Design: Experimental study using porcine eyes. Methods: Profiles of the stress wave amplitudes and enucleated human eyes a long the axis of symmetry of porcine eyes and enucleated human eyes were me asured using a miniature piezoelectric transducer, The ablation parameters, fluence, and ablation diameters were varied within the range of clinical a pplication, Main Outcome Measures: Stress wave amplitudes generated during photoablatio n, Results: The stress waves pass through a pressure focus located in the post erior lens and anterior vitreous, where amplitudes of up to 100 atm were me asured with a 6-mm or larger ablation zone, Posterior to this focus, the st ress wave amplitudes rapidly decrease to less than 10 atm at the retinal si te. Small diameter excimer laser spots (less than or equal to1.5 mm) produc e a declining stress wave with no pressure focus at the lens and anterior v itreous. Conclusions: Stress waves may be potentially hazardous to anterior structur es of the human eye, including the corneal endothelium, lens and anterior v itreous face. They peak at the lens and vitreous with a broad beam, but not with small spot laser ablation, At posterior retinal and subretinal struct ures, they may be considered harmless. Ophthalmology 2001;108:1070-1074 (C) 2001 by the American Academy of Ophthalmology.