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AA Moshfeghi, GA Peyman, M Genaidy, DM Moshfeghi, F Gharamani, S Yoneya; Threshold Parameters for Creating Transpupillary Thermotherapy (TTT) Lesions in Normal Rabbit Fundi: Influence of Indocyanine Green (ICG), Ocular Compression, and Pigmentation . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4407.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To determine the transpupillary thermotherapy (TTT) parameters needed to induce funduscopically and angiographically visible lesions in pigmented and non-pigmented (albino) rabbit fundi. To evaluate the effects of intravenous (IV) indocyanine green pretreatment, ocular compression, and fundus pigmentation on TTT. Methods: Two pigmented rabbits and 5 albino rabbits were used in this study. In each group, an 810-nm diode laser with slit-lamp delivery system and Goldmann macular lens was used to provide a spot size of 2.0 or 3.0 mm for 1-3 minutes of laser exposure with or without ocular compression sufficient to blanch the optic nerve head. Power ranged from 80-200 mW in pigmented rabbits and from 750-1800 mW in albino rabbits. ICG (0.4-3.0 mg/kg) was injected IV 1 to 9 minutes prior to TTT application in some areas in pigmented rabbits and 1 to 10.5 minutes prior to TTT application in some areas in albino rabbits. Results: Pigmented rabbits/2 mm spot size/1 minute duration: 120-150 mW without compression and 80-100 mW with compression was needed to produce visible and angiographic lesions. Pigmented rabbits/3 mm spot size: threshold lesions appeared with 200 mW at 2 minutes and 150 mW at 3 minutes (both without compression); compression decreased the 2 minute threshold to 140 mW; IV ICG (3 mg/kg) given 7 minutes prior to TTT reduced the 2 minute threshold to 80 mW. Albino rabbits/2mm spot size/1 minute duration: 1500 mW without compression and 1400 mW with compression achieved threshold levels. IV ICG (at least 1.4 mg/kg) lowered the threshold to 750 mW, which was largely irrespective of increased dose or of varying the time elapsed from ICG injection to TTT initiation. Conclusion: Threshold parameters for TTT are largely influenced by fundus pigmentation and ICG pretreatment (photosensitizing effect) and less dependent on ocular compression.
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