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.