Optoacoustical tissue alteration for optimizing laser cyclophototoagulation. Transscleral detection of laser-induced optoacoustical pressure transients

Background. Considerable problems occur in transscleral laser cyclophotocoa gulation concerning energy dosage. We investigated the feasibility of local izing the ciliary body by the detection of thermoelastic pressure transient s and of supervising on-line the degree of tissue damage during treatment. Method. We used a specially designed handpiece to apply short pulsed laser radiation with low energy levels to enucleated bulbs of rabbits. With an ad justed pressure transducer we examined acoustical transients generated in t he area of absorption of the ciliary muscle or the pigmented epithelial lay er and measured axial resolution of the method at various distances to the corneoscleral limbus. Results. We detected acoustic transients that allowed rough localization of the target area. A marked change in signal was recorded with increasing le vel of ciliary destruction. Conclusion. This procedure can serve as an essential tool in the on-line su pervision of the coagulation process. The laser parameters can thus be adju sted optimally to the progress of the treatment.