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J.D. Wolfe, J. Baffi, G. Byrnes, K.G. Csaky; Requirement for Indocyanine Green as a Photodynamic Agent in Diode Laser Closure of Retinal and Choroidal Vessels . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1782.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: High-speed indocyanine green angiography (HS-ICGA) has demonstrated the presence of extrafoveal choroidal feeder vessels supplying areas of choroidal neovascularization (CNV) in many patients with neovascular age-related macular degeneration (AMD). Therefore, permanent selective laser closure of these feeder vessels using an extrafoveal application of a small spot beam represents a possible therapeutic approach for CNV. However, little is known of the mechanism of direct vessel closure with thermal or photodynamic laser energy. The following study was performed to determine the effects of diode (810 nm) and ICG-enhanced diode treatment on closure of both choroidal and retinal vessels in patients with neovascular AMD and in rat retinas. Methods: Feeder vessels in patients with neovascular AMD was detected by HS-ICGA and localized by thin plate splines registration of corresponding red-free retinal images. Vessels were treated with milli-pulsed diode laser photocoagulation and post-treatment effects on the feeder vessels were monitored by both immediate and weekly HS-ICGA. The retinal arterioles of either non-pigmented Lewis (LE) or pigmented Brown-Norway (BN) rats were treated with either diode laser alone or immediately after an intravenous injection of indocyanine green dye (ICG) at various doses. Closure of the retinal vessel was determined by perfusion of the retinal vasculature with fluorescein isothiocyanate dextran (FITC-dextran) and direct retinal flat mount observation. Results: Milli-pulsed diode laser was successful in choroidal feeder vessel closure in humans. However, vessel reperfusion was typically seen 3 – 7 days after the treatment. In pigmented BN rats, diode laser alone achieved retinal vessel closure but with reperfusion within one week. However, in non-pigmented LE rats, milli-pulsed diode laser did not achieve vessel closure despite maximizing energy and pulse duration but was successful after intravenous administration of ICG at a dose of 5 mg/kg. Conclusions: The present study demonstrates that diode laser alone is not successful as vessel closure but requires the presence of extraluminal pigment to achieve temporary vessel closure. However, ICG-enhanced photodynamic therapy results in a more permanent vessel closure in the absence of pigment suggesting a direct intraluminal effect. On-going studies will determine the usefulness of photodynamic feeder vessel closure for neovascular AMD.
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