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MS Ibarra, B Madjarov, C Glazer-Hockstein, MA Mainster, AM Maguire, J Bennett, MJ Tolentino; Determination of Retinal Thermal Dosimetry from Transpupillary Thermotherapy . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4412.
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Purpose:Transpupillary thermotherapy (TTT) is a method of delivering localized heat to the posterior pole using a subthreshold, infrared laser which is currently being evaluated as a treatment modality for choroidal neovascularization in macular degeneration. The purpose of this study is to determine the effect of pigmentation, choroidal blood flow, and subretinal blood on TTT-induced temperature change on the retina. Methods:Direct retinal temperature measurements were performed using an ultra-fine thermocouple on New Zealand White (albino) and Dutch Belted (pigmented) rabbit eyes undergoing TTT. TTT was performed with an 810nm diode laser on a slit lamp delivery system using a 1.2 mm spot, 60 seconds duration, and a range of power settings between 50-1000 mW. Temperature measurements were taken in eyes in the presence or absence of choroidal blood flow and in eyes with subretinal blood. Results:Threshold power settings for albino and pigmented rabbits were 950 mW and 90 mW, respectively. When albino subthreshold power settings were applied to pigmented rabbits, temperature rise was greater than 1.5 fold higher than that of albino rabbits. Temperature rise in albino eyes with subretinal blood was at least two-fold higher than in eyes without subretinal blood. There was no change in temperature rise when choroidal blood flow was occluded. Conclusion:Performing TTT on pigmented individuals or in the presence of subretinal blood should warrant a relative decrease in power setting. Additionally, the presence or absence of choroidal blood flow does not alter TTT temperature rise.
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