Hematoporphyrin Photoradiation Therapy for Iris Neovascularization

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Abstract
• Photoradiation therapy is a new technique currently under clinical investigation for the treatment of a variety of solid malignant tumors. The technique involves intravenous (IV) administration of hematoporphyrin derivative, a photosensitizing compound that is preferentially retained by malignant cells, and photoactivation of a neoplasm with red light (630 nm) to obtain selective destruction of cancer cells. A modification of this technique was used to treat iris neovascularization produced in a primate model of retinal vein occlusion. Following IV injection of hematoporphyrin derivative, the anterior surface of the iris was exposed to red light for 30 to 45 minutes. In the four eyes treated, there was a marked reduction of fluorescein leakage from the neovascular tissue within 24 hours following treatment. Histologic examination of two eyes demonstrated a selective response of the iris neovascularization to this therapy, with apparent preservation of surrounding tissue.