Subtraction ICG angiography in Harada's disease.

Abstract

The significance of indocyanine green (ICG) angiography (ICGA) in Harada's disease still awaits clarification in many respects. This study investigates the details of choroidal lesions observed in Harada's disease by the subtraction method. Eight patients with Harada's disease were followed with ICGA. ICG angiograms were obtained with a Topcon high resolution digital fundus camera and processed with a Topcon IMAGEnet computer system. Image subtraction was conducted for analysing serial angiograms taken at about 2 second intervals during the dye transit phase and those taken in the early and middle phases of angiography. Standard ICG images of acute stage disease showed delayed choroidal filling in the early phase. Mid phase angiograms showed areas with bright fluorescence of variable intensity, indicating intrachoroidal ICG leakage. With image subtraction of angiograms with an interval of seconds the choroidal vessels could be imaged sequentially, with the choroidal arteries visualised first, followed by the definition of the choriocapillaris and then the choroidal veins. The choroidal veins with delayed filling were visualised as positive images in serial subtraction angiograms. Subtraction with an interval of minutes showed uneven background fluorescence and bright fluorescence corresponding to the areas of intrachoroidal ICG leakage. After the disease subsided with steroid therapy, angiography revealed an improvement in delayed choroidal filling. Image subtraction by the second allowed a clear visualisation of improved choroidal venous filling, while subtraction by the minute showed homogeneous background fluorescence, eliminating brighter areas. Subtraction ICGA demonstrated that delayed filling of the choroidal veins of varying severity occurs in association with hyperpermeability of the choroidal vessels in the course of Harada's disease.