ADVANCES IN PHOTODYNAMIC THERAPY USING INDOCYANINE GREEN

Michel Eid Farah, R. A. Costa, J. A. Cardillo (Sao Paulo)

1. Experimental study

To evaluate the potential of photodynamic therapy using indocyanine green for occlusion of choroidal neovascularization, we authors studied efficiency and collateral damage of photodynamic therapy-induced photothrombosis in the rabbit choriocapillary layer. The delivery system consisted of a modified infrared diode laser tuned to 810 nm, near the maximum absorption peak of indocyanine green. Choriocapillary occlusion was achieved at indocyanine green doses of 10 and 20 mg/kg and a radiant as low as 6.3 J/cm? When photodynamic therapy was performed with indocyanine green doses of 10 mg/kg, damage to the neural retina was minimal. Membrane targetability, hydrophilic and fluorescent properties, and activation at 805 nm suggest indocyanine green as a potential photosensitizer for choroidal neovascularization.

2. Clinical Studies

Classic choroidal neovascularization in age-related macular degeneration
A prospective study was conducted to eveluate the clinical features, treatment results, and complications of 8 patients with predominantly classic subfoveal CNV who were treated with a single session of i-PDT and followed for at least a 3 months period. The final visual acuity was the same in four eyes (59 %), increased in 3 eyes (37,5 %) and decreased in 1 eye (12,5 %) by 3 months of follow-up.

Occult choroidal neovascularization in age-related macular degeneration
A prospective, noncomparative case series, was undertaken to evaluate the efficacy of photodynamic therapy using indocyanine green and 810 nm light for the treatment of occult subfoveal choroidal nevascularization due to age-related macular degeneration. In eighteen patients (20 eyes) during the follow-up period of 12 weeks. Nineteen eyes (95 %) exhibited na increase or stabilization of visual acuity in a follow-up period of 3 months. Mild visual loss occurred in one patient due to the development of a classic lesion. Hemorrhagic pigment epithelium detachment (3 eyes) was the major complication related to the procedure.

Idiopathic subfoveal choroidal neovascularization
A prospective noncomparative case series. Four patients (5 eyes) with idiopathic CNV were treated with indocyanine green and 810 nm light. Follow-up time ranged from 4 to 6 weeks (mean 11,5 weeks). Four eyes (80 %) demonstrated minimal leakage on fluorescein angiography and OCT. Visual acuity testing, fluorescein and indocyanine green angiography as well as optical coherence tomography (OCT) were used to evaluate the results of all treatment since these preliminary clinical studies.


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