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Matthias H. J. Krause, MD; Jing Xiong, MD; Evangelos S. Gragoudas, MD; Lucy H. Y. Young, MD, PhD

Arch Ophthalmol. 2003;121:357-363.

Objective  To evaluate the effect of a new infrared laser in the destruction of pigmented choroidal melanomas.

Methods  B16F10 melanomas were implanted in the subchoroidal space of 64 rabbits (tumor height, 2.0-4.0 mm). Laser radiation from an Nd:yttrium-lanthanum-fluoride laser (1047 nm) was delivered as a focused (beam waist, 25 µm; irradiance, 100 kW/cm²) raster-scanned transpupillary beam. To investigate melanin heating, treatment with focused light was compared with collimated light (beam waist, 2 mm; irradiance, 16 W/cm²). Fine-wire thermocouples were implanted at the base of 3 tumors for in vivo temperature measurements. Untreated animals were used as controls.

Results  Of 64 animals, 27 received a single treatment with focused 1047-nm light. The rate of complete tumor eradication was 91% (10 of 11 animals) at a dosage of 125 J/cm² and 75% (9/12) at 63 J/cm² to 87 J/cm². The eradication rate dropped to 25% (1 of 4) at 38 J/cm² or less (P<.001). Continuous tumor growth was observed in all animals treated with collimated radiation and in untreated controls. Temperature measurements indicated that tissue heating at the tumor base was more rapid at 1047 nm than at 805 nm.

Conclusions  These data suggest that a single treatment with a focused, raster-scanned beam at 1047 nm may play a role in the destruction of pigmented choroidal melanoma. Focused irradiation at 1047 nm may provide more effective submillisecond heating of melanin than collimated irradiation, resulting in immediate photothermal disruption of tumor cells.

From the Retina Service and the Laser Research Laboratory, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston.
The authors have no commercial or proprietary interest in the products and companies mentioned in this article. They do not have any financial interest and do not receive payment as consultants, reviewers, or evaluators.

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