Ophthalmology and Visual Sciences

  • Indocyanine Green (ICG) Angiography

    ICG is used to acquire an angiogram of the choroid. The choroid is the layer of blood vessels and connective tissue between the sclera (white of the eye) and retina. It supplies nutrients to the inner parts of the eye.

    A procedure similar to fluorescein angiography, but ICG angiography uses Indocyanine Green dye, which fluoresces in the infra-red (non-visible) light. The infra-red wavelenths have the ability to penetrate the retinal layers making the circulation in deeper layers visible when photographed with an infra-red sensitive camera.

    ICG is injected intravenously and flows through the body to reach the choroidal and retinal circulation. Due to its nature ICG stays in the retinal and choroidal vessels, this allows the distinct outlines of the vessels of the choroid to be seen and identified. ICG is sometimes used to complement fluorescein angiography (FA). FA is often referred to retinal angiography while ICG angiography is referred to choroidal angiography.

    ICG was first used in 1969[1] but was not brought into the practical clinical setting until 1992.[2]

    Case Example:

    In the case of a patient with 20/100 vision, the fluorescein angiogram demonstrated leakage of fluorescein dye over a large area near the fovea. Traditional treatment would dictate that the entire area of leakage be treated with laser surgery. The treatment of this lesion would cause an instant decline in vision to 20/400.

    The ICG angiography, performed on the same day, reveals a pinpoint leak not visible with fluorescein angiography. Focal treatment based on the ICG angiogram caused an increase in vision from 20/100 to 20/80.


    Click any image for higher resolution
     
    ipre-colorfundus-thumb.jpg

    Pre-Treatment Color Photograph

     ipre-fa-1-thumb.jpg                      ipre-fa-2-thumb.jpg                      ipre-fa-3-thumb.jpg

      Early Phase FA                        Mid-Phase FA                        Late Phase FA

    Pre-Treatment Fluorescien Angiogram

      ipre-icg-1-thumb                    ipre-icg-2-thumb.jpg                    ipre-icg-3-thumb.jpg

       Early Phase ICG                        Mid-Phase ICG                    Late Phase ICG

    Pre-Treatment ICG Angiogram


    After treatment the laser scar is visible on the color fundus photograph. Both the fluorescein and the ICG angiograms show no leakage of dye demonstrating that the focal treatment was effective.


     

    ipost-colorfundus-thumb.jpg

    Post-treatment Color Photograph

      ipost-fa-1-thumb                    ipost-fa-2-thumb.jpg                    ipost-fa-3-thumb.jpg

       Early Phase FA                        Mid-Phase FA                        Late Phase FA

    Post-treatment Fluroescein Angiogram

      ipost-icg-1-thumb                    ipost-icg-2-thumb.jpg                    ipost-icg-3-thumb.jpg

       Early Phase ICG                    Mid-Phase ICG                        Late Phase ICG

    Post-treatment ICG Angiogram

    Photographs by UIHC Opthalmic Imaging Staff


    References:

    1. Kogure K, Choromokos E. Infrared absorption angiography. J Appl Physiol. 1969;26(1):154-7.
    2. Yannuzzi LA, Slakter JS, Sorenson JA, Guyer DR, Orlock DA. Digital indocyanine green videoangiography and choroidal neovascularization. Retina.1992;12(3):191-223.