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J.I. Loewenstein, S.R. Montezuma, N. Waheed, J.F. Rizzo; Use of Verteporfin Photodynamic Therapy to Control Choroidal Bleeding for Implantation of a Retinal Prosthesis . Invest. Ophthalmol. Vis. Sci. 2003;44(13):5065.
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Purpose: Subretinal placement of prosthetic electrodes behind the posterior retina is most directly accomplished with a tran-scleral approach, but incision through the choroid can lead to significant hemorrhage. The aim of this study was to determine if photodynamic therapy would close choroidal vessels if the laser was applied ab externo through the opening of a scleral flap. Methods: Nine eyes of nine Dutch-Belted rabbits were used. A scleral flap was made to expose the choroid. Intravenous (N=5) or topical Verteporfin (N=1) dye was given, then diode laser (600mW/cm2, 0.3 cm, 150 to 300 J/cm2) light was applied for 250 or 500 sec. Control experiments (N=3) were prepared by withholding either the laser or Verteporfin. Fluorescein (FA) and indocyanine green (ICG) angiography, and histology were performed to assess choroidal vessel closure. Results: Twenty-four hours post-surgery FA and ICG angiography showed complete choroidal closure within the treated area in the 4 eyes with 500 sec of treatment, but only after the dye had been given intravenously (not topically). Choroidal closure was not immediate, but was evident in the four eyes when angiography was performed 24 hours post-treatment. Complete choroidal closure was confirmed in all four eyes by histology, which within treated areas revealed: damage to the retinal pigment epithelium in two eyes; disorganization of the outer nuclear layer in two eyes; and pyknosis of the outer retina in two eyes. Some or all of these rheological and histological changes were observed in all eyes, even in areas far from the scleral flap. The middle and inner retina were normal in all eyes. No closure of large choroidal vessels was seen in the eye that received 250 sec of treatment. Two control eyes showed choroidal congestion by angiography, although there was no histological alteration. Conclusions: Photodynamic therapy using IV Verteporfin can be used to close normal choroidal vessels without causing significant retinal damage to the middle or inner retina, which makes this technique potentially useful to control bleeding in ab externo implantation of a retinal prosthesis
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