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RP Rodrigues, E Magalhães, MB Nehemy, C Campos, E Passos, M Salgado; Clinic and Histopathologic Study of Transpupillary Thermotherapy in Pigmented Rabbits . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2621.
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Purpose: To evaluate the macroscopic and histologic effects induced by temperature elevation of transpupillary thermotherapy (TTT) in retina and choroid of pigmented rabbit eyes. Methods: TTT was delivered in 40 eyes of pigmented rabbits, using the diode laser of 810 nm wavelength. Each eye received 4 laser pulses below the medullary fibers layer, with fixed spot size of 3000 micra. The exposure time was variable from 17 to 66 seconds, and interrupted if there was any retinal change during the procedure. The initial power was fixed in 300 mW and reduced 20, 40, and 60%. When retinal whitening was observed on the retina, 20% of laser pulse was reduced, until there was no macroscopic alteration. Histologic examination by light microscopy was performed 24 hours and 4 weeks after treatment. Results: All lesions with even minimal macroscopic whitening during TTT showed retinal and choroidal damage. 24 h after TTT the histologic study showed acute retinal necrosis, intersticial edema and choroidal vessels thrombosis. Four weeks after TTT, the histologic study of the lesions showed a glial scar. Conclusion: Clinical and histologic examinations by light microscopy showed correlate results. This experimental study in pigmented rabbits shows that it is important to interrupt the TTT application before any clinical change in the fundus.
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