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F.M. Damico, J. Xiong, E.S. Gragoudas, L.H. Young; Destruction of Pigmented Choroidal Melanoma Using Trans-scleral PDT . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4981.
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Purpose: There are many treatment modalities for the management of choroidal melanoma but each one has its limitations. In our laboratory, we have demonstrated successful destruction of pigmented choroidal melanomas with trans-pupillary photodynamic therapy (PDT). The aim of this study is to determine whether PDT applied transclerally can be effective in tumor destruction. Methods: Pigmented choroidal melanomas were established in New Zealand rabbits as previously described. Scleral attenuation of laser energy was measured across 1.0 cm2 sections of fresh sclera as laser spot were delivered to the external scleral surface via a fiberoptic probe coupled to a diode laser tuned to 689 nm. Next, using the same laser delivery system, normal eyes were treated in vivo immediately after injection of benzoporphyrin derivative (BPD 2 mg/kg) and tumor-bearing eyes were treated 15 minutes after the injection. Fluences of 50, 100, 200, 300 and 400 J/cm2 were used. For control, eyes were treated with laser only. Animals were sacrificed immediately after treatment, and the eyes were examined by light microscopy. Results: Fresh sclera attenuated laser energy by 70-77%. The choroid in the treated areas all showed markedly dilated vessels packed with swollen erythrocytes, suggestive of vascular closure. In tumor-bearing eyes, dilated intratumoral vessels were seen at the base of the tumor. At 400 J/cm2, markedly dilated intratumoral vessels were found 700 µm deep from the inner surface of the sclera. There were no vascular changes in eyes treated with laser alone. Conclusions: Although a high degree of laser energy attenuation is caused by the sclera, our results suggest that choroidal vascular closure can be achieved by trans-scleral PDT. In tumor-bearing eyes, the closure of the vascular supply at the base of the tumor may have an additive role in the management of thick tumors.
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