Hematoporphyrin derivative (HpD) photoradiation therapy (PRT) is currently being examined for the treatment of intraocular tumors. HpD is taken up in malignant tissue, and tumorcidal action can be induced when HpD is activated with visible red light. Preclinical studies have been performed to examine the pharmacology of HpD and the toxicology of HpD PRT in both normal and malignant structures in the eye of pigmented rabbits. A dye laser system has been utilized to generate red light (630 nm) for localized irradiation of ocular tissue following intravenous administration of HpD. Tissue distribution of HpD was measured by an acid extraction procedure. Vascular structures of the eye, such as the choroid, iris, and experimental ocular tumor, retained significant levels of HpD. In addition, there is a transient uptake of HpD in the aqueous (Fig. 1). Nonvascular structures such as the cornea and lens did not take up HpD. Toxicity studies demonstrated that HpD administration (1–10 mg/kg) followed 48 h later with a transpupil irradiation of red light (630 nm, 40–90 J/cm2) resulted in well-defined areas of retinal damage within the treatment field. The lenses of 18 eyes have remained clear during a 24 month follow-up. Tumor response following HpD PRT is rapid and characterized by massive vascular disruption and tumor tissue necrosis. Currently, 10 patients with intraocular tumors (retinoblastoma or uveal melanoma) have received HpD PRT. The preliminary clinical results will be described.

© 1984 Optical Society of America

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