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Y Ito, T Sodeyama, K Mori, K Anzail, Y Takita, D Imai, M Shibuya, S Yoneya, DM Moshfeghi, GA Peyman; Comparative Study of Visible and Infrared Light in Transpupillary Thermotherapy . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4419.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To study a potential effect of transpupillary thermotherapy (TTT) on the retina and choroid using laser wavelengths of 635 nm and 810 nm. Methods: We performed diode laser irradiation on eyes of Japanese monkeys. Seven eyes were treated with a 635-nm wavelength and 5 eyes with the 810-nm wavelength. An area of the posterior fundus 1 mm in diameter was irradiated with 635 nm with varied exposure durations ranging from 30 to 80 seconds, eventually achieving 20, 50, and 79.2 J/cm2. Irradiation with the 810-nm diode laser was also performed on the posterior fundus 2 mm in diameter. The duration was set at 60 seconds and the total energy alternated between 96, 115, and 153 J/cm2. Clinical evaluations were made with funduscopy and fluorescein and indocyanine green angiography (FA and ICG) before and after the treatment. The animals were sacrificed either immediately or 2 weeks after the treatment and the eyes were processed for histopathological study. Results: Laser lesions were not visible by funduscopy or angiography throughout the follow-up period. The light microscopy study, however, revealed that the outer nuclear layer showed pyknotic changes which were more significant with the 810-nm wavelength. The inner segments of the photoreceptors (IS) were swollen and vacuolated. The retinal pigment epithelium (RPE) also demonstrated vacuoles. Using electron microscopy, the cytoplasm of the IS appeared watery and had vacuolated mitochondria. The intercellular spaces of the IS were enlarged. The mitochondria in the RPE were vacuolated. The choriocapillaris and large choroidal vessels were attenuated or closed in some areas 2 weeks after treatment. These findings were common at all power settings with both the 635- and 810-nm laser wavelengths. Conclusion: TTT with 635- and 810-nm wavelength diode lasers occluded choroidal vessels; however, some damage to the inner retina occurred. Therefore, the indications and irradiation settings for TTT must be chosen with careful consideration.
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