INTERNAL ABLATIVE SINOSTOMY USING A FIBER DELIVERED Q-SWITCHED CTE - YAG LASER (2.69-MU-M)

Current trends of laser technology towards low-thermal photoablative p ulsed mid-infrared lasers open new, more adequate approaches to experi mental surgical procedures which have already been evaluated in the pa st. Transcorneal laser ablation of the trabecular meshwork (internal s inostomy) in human autopsy eyes was performed with a Q-switched CTE:YA G laser (wavelength: 2.69 mum, pulse width: 1 mus). Beam delivery was achieved with conventional optical quartz fibers (Low-hydroxy-fused-si lica: 0,3 ppm, 50 cm length, 200 mum diameter). Light- and scanning-el ectron-microscopy were used for histological examination and micromorp hological analysis. By applying two laser pulses (6 J/cm2) to the func tional trabecular meshwork, a round sinostomy with a diameter correspo nding to the diameter of the fiber-tip was achieved. It was possible t o set several internal sinostomies into the chamber angle opposite to the entering paracentesis of the laser fiber-tip. Collateral thermal t issue alteration reached up to 50 mum, and since fiber-tip contact was maintained during laser application, thermal tissue alteration was al so found around the opposite wall of Schlemm's canal. At higher energy fluences mechanical (disruptive vaporization) effects were significan tly enhanced. It can be concluded, that low-thermal pulsed mid-infrare d lasers are adequate instruments to perform transcorneal trabecular a blation (abinterno sinostomy). The laser used in this study (CTE:YAG) bears the advantage that its radiation can easily be delivered in conv entional optical quartz fibers.