Recently iridectomy using an argon or Nd-YAG laser to treat narrow angle glaucoma has become popular, and is now the procedure of choice over the standard surgical technique. However, the shock wave of the Nd-YAG laser causes hemorrhage in almost all cases and the high energy level of the Nd-YAG laser, which is required for iridectomy, causes injury to the lens and cornea. Furthermore, there is a tendency toward closure of the iridectomy site after argon laser application. We performed iridectomies by a combined application of argon and Nd-YAG lasers in pigmented rabbits to improve iris bleeding, iridectomy patency, and lens and corneal damage. The iridectomy patency and the lens and corneal damage were examined with a scanning electron microscope. The rabbits that underwent laser iridectomies with only the Nd-YAG laser were used as a control group. Based on the results, it can be concluded that laser iridectomy by a combined application of argon and Nd-YAG lasers results in a lower rate of bleeding, a higher rate of patency, and less damage to the lens and cornea as compared with iridectomy performed by Nd-YAG laser only.
Animals ; Cornea/ultrastructure ; Endothelium, Corneal/ultrastructure ; Eye Hemorrhage/etiology ; Iris/blood supply/*surgery/ultrastructure ; *Laser Therapy/adverse effects ; Lens, Crystalline/ultrastructure ; Microscopy, Electron, Scanning ; Rabbits ; Random Allocation

Iris neovascularization was produced in rabbits by hypotony following repeated aspiration of the vitreous. The hypotony was produced after 0.3 ml of vitreous fluid was aspirated using a 25-gauge needle through the pars plana of 10 rabbits. For the histochemical study, horseradish peroxidase(HRP) was injected through the ear lobe vein. After fixation of the iris tissue, the tissue was treated with diaminobenzidine and examined with both light microscopy and transmission electron microscopy. The newly-formed vessel was abundant, particularly on the upper stroma of the iris. The new vessel formation was evident due to the proliferation of endothelial cells, which may have been derived from preexisting iris vessels. The endothelial cells of the newly-formed vessels revealed prominent villous processes into the vascular lumen, formation of the marginal flap, numerous fenestrations in the endothelial junction, and reaction product onto extravascular space by the cytochemical electron microscopy. These results suggest that hypotony in the rabbit produces the disruption of the blood-iris barrier and the balance between angiogenesis-antiangiogenesis modulation.
Animals ; Biological Transport, Active ; Disease Models, Animal ; Horseradish Peroxidase/diagnostic use ; Iris/*blood supply/*ultrastructure ; Iritis/*pathology ; Neovascularization, Pathologic/*pathology ; Rabbits ; Vitreous Body/surgery