Transscleral Ciliary Body Photodynamic Therapy Using Phthalocyanine and a Diode Laser: Functional and Morphologic Implications in Albino Rabbits

Abstract

To evaluate the morphologic and functional effects of ciliary body photodynamic therapy (PDT) using phthalocyanine and a diode laser. The upper half of the left eye ciliary body of 16 albino rabbits was irradiated transsclerally using a 670-nm diode laser (400 mW/cm2) after intravenous injection of phthalocyanine (6 mg/kg). The animals were observed for a maximum of 2 months by means of tonometry, biomicroscopy, and fundus examination. At the end of the follow-up period, they were killed and their eyes were prepared for light and electron microscopy. Transscleral PDT resulted in intraocular pressure (IOP) reduction in the treated eye, which lasted about 2 weeks. During this time, the treated eye had IOP values that were significantly lower than its baseline IOP values and the IOP values of the untreated eye (P < .05). One month after the procedure, the IOP had returned to baseline values. Histologic examination revealed vascular endothelial cell damage causing vascular thrombosis in the treated areas. The architecture of the two ciliary epithelium layers showed a significant abnormality. Disappearance of epithelial apical junction complexes and loss of the normal b-cytomembrane enfolding were observed in the course of electron microscopic examination. Large intercellular spaces between epithelial cells were noticed. All of these changes had subsided by the end of the second postoperative month. Transscleral phthalocyanine-mediated PDT with the parameters used in this experiment results in significant but temporary functional and morphologic alterations in the ciliary bodies of albino rabbits.