VITREORETINAL ABLATION WITH THE 193-NM EXCIMER-LASER IN FLUID MEDIA

Purpose. To ablate retina and vitreous membranes using the 193-nm argo n fluoride excimer laser in a fluid medium. Methods. A special deliver y system for the 193-nm excimer laser was developed that enabled the d elivery of the laser into high-absorption liquid environments. The sys tem was tested on the retina in an in vitro cup preparation of cow's e yes, and also in vivo on retina and vitreous membranes of rabbit eyes. The depth of cut as a function of laser energy was determined for an ablating needle with a 0.25-mm exit diameter. Results. Gentle cutting of retinal tissue and of vitreous membranes was obtained in an energy range of 0.075 to 0.25 mJ/pulse. At the energy level of 0.075 mJ/pulse , four pulses were required for full-depth cut formation in rabbit ret ina, whereas at energy levels greater than 0.17 mJ/pulse, one pulse wa s sufficient for full-depth cut formation. The maximal rate of cutting achieved for the bovine retina was 2 mm/sec at a 20-Hz repetition rat e of the laser. Ablation occurred only when the tip was held in contac t with the tissue. Conclusions. The technology described herein appear s to be advantageous and applicable to a variety of vitreoretinal surg ical procedures.