Transpupillary thermotherapy alone and enhanced by standard doses of indocyanine green in pigmented rabbits.

BACKGROUND AND OBJECTIVE: To evaluate the chorioretinal effects of transpupillary thermotherapy (TTT) and TTT enhanced by standard doses of indocyanine green (ICG) in pigmented rabbits. MATERIALS AND METHODS: In 25 eyes, two retinal areas were irradiated using identical subthreshold diode laser irradiation. The subthreshold diode laser irradiation level was first determined using the other eye. ICG (0.5 mg/kg) was injected before irradiation of the second area. Red-free photographs, fluorescein angiography, and ICG videoangiography were performed after TTT. Specimens were prepared for light microscopy. RESULTS: In 35% of the cases, ICG videoangiography revealed a hypofluorescent spot in the area irradiated after injection of ICG that disappeared after ICG re-injection. None of the areas irradiated before ICG injection were hypofluorescent. Red-free photographs and fluorescein angiography were normal in most cases. Light microscopy demonstrated patent choriocapillaris and choroid in most areas. CONCLUSIONS: Subthreshold TTT, whether enhanced by ICG or not, did not cause significant choroidal or choriocapillaris vascular occlusion. Standard doses of ICG had no significant effect on TTT.