Surgical Fibers - vitreoretinal Ablation With the 193-nm Excimer Laser in Fluid Media

Keywords:surgical fibers, laser fiber,  Time:03-03-2016

Several attempts were already undertaken of tractionless removal of vitreoretinal membranes using various types of lasers guided through optical surgical fibers.1"3 The approach using CCV and Er-YAG3 lasers that are strongly absorbed in water has encountered difficultly, in that the effect of the laser on the treated tissue is too distant: the retina was damaged when the laser probe was located approximately 2 mm from its surface. The 308-nm xenon chloride excimer laser was also reported to be capable of cutting the vitreoretinal membranes,2 but this wavelength is known to cause severe hazards to the cornea, lens, and retina.4 As a result, all these approaches have failed to achieve widespread acceptance.

The 193-nm argon fluoride (ArF) excimer laser is known for its ability to ablate biologic tissue with minimal damage to the surrounding tissue.5'6 A l-um penetration depth of this radiation in most biologic materials allows for exceptional control of ablation depth.6'7 Furthermore, the ArF excimer laser has been shown to have no mutagenic effects on mammalian cells.8"10 Nonetheless, despite these advantages, this laser has been widely accepted in medicine only for refractive surgery.11 The lack of microsurgical applications of the 193nm excimer laser in liquid environments arises mainly from the absence of a convenient delivery system, because this laser does not pass efficiently through optilimited the use of this laser to applications in air and to relatively dry tissues such as the cornea. The development of a delivery system capable of transmitting the 193-nm laser beam in a fashion suitable for microsurgery in a high-absorption liquid environment has been the object of several years of experimentation at the Hadassah Laser Research Center. In a preliminary investigation, we described a system that was capable of working in a gas environment.13 With this system, it was possible to photoablate retinal tissue in an air-filled eye in a precise fashion without heat deposition in the surrounding tissue. Working in the air-filled eye, it was impractical to remove vitreoretinal membranes, a major objective of these investigations.

A few years ago, we applied the 193-nm excimer laser, delivered into a liquid environment through glass micropipettes filled with air, to drilling holes 4 to 8 fim in diameter in the zona pellucida of oocytes.14 Although this delivery system suits well the tiny scale of microsurgery in liquid environment, it can not withstand the energy fluence and number of pulses required for vitreoretinal membrane removal. Recently, we have developed a type of laser tip that allows the 193-nm excimer laser to be applied to microsurgery in the high-absorption liquid environment. In this article, we present preliminary in vitro and in vivo data on this intravitreal device capable of cutting retinal and membranous tissue in the fluid environment of a live eye in a fast, precise, and reproducible fashion.