PHYSICAL ACTION MECHANISMS IN SKLEROSTOMY

Various sclerostomy procedures, performed ab interno and ab externo ha ve found increasing interest for some time. With few exceptions, invas ive procedures are described, in which laser energy is transmitted by means of specially designed fibers and probes ab interno and ab extern o to the perforation site. Laser energy sources, ranging from the UV t hrough the visible to the IR range have been described. Thus far, no d etailed models quantifying the ablation mechanism of such sclerostomy procedures have been published. All such procedures have in common tha t the wavelength of the laser should be matched to water absorption ba nds. Now more sophisticated models describing the action mechanism of various lasers begin to emerge. A system described by us takes advanta ge of the high efficiency of rapid steam explosions occurring in a clo sed space, i.e. in the region delimited by the probe end and the fistu la bottom. The high efficiency of such mechanisms has been verified in model experiments on porcine eyes in vitro. Electron microscopical re sults also show that the amount of thermal damage is negligible and th at there is very little wavelength-dependence. This permits the adopti on of ,,common'' laser energy sources such as diode and Nd:YAG lasers. The clinical survival probability of fistulas as related to the amoun t of collateral damage is controversial.