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Ocular angiography

Angiography is performed by injecting a dye into a vein in the arm and then taking a succession of photographs of the back of the eye.

The dye is fluorescent; that is, it has the property of changing light from one colour to another. The photographs are taken using a flash and a filter of the appropriate colours. The dye can therefore be seen shining brightly as it passes through the arteries and veins and as it leaks through any abnormal areas.

There are two kinds of angiography: fluorescein angiography and indocyanine green angiography, which use blue and red light respectively.

Fluorescein angiography

Fluorescein fundus angiography demonstrates the retinal vasculature and abnormalities in the retina and retinal pigment epithelium. The injected fluorescein dye tends to cause yellowing of the skin and urine for a few hours and about one in ten patients experience transient nausea, although vomiting is rare. About one in 2000 patients develops an allergic reaction, which very rarely is fatal (i.e., in about one in two hundred thousand patients).

 

Fig4-3

Fluorescein angiogram of a choroidal melanoma in the eye, showing the dye leaking from the tumour surface. The overlying retinal vessels are also highlighted.

 

Indocyanine green angiography

Indocyanine green angiography demonstrates sub-RPE abnormalities better than fluorescein angiography, because the red light penetrates deeper.