Fig. 7.4 This patient presented with a sudden change in visual acuity. She was found to have CNV secondary to age-related macular degeneration complicated by rips in the RPE (asterisks) and chorioretinal folds (arrowheads) as seen in this autofluorescent image

Fig. 7.5 Color montage photograph of a patient who had large subretinal and sub-RPE hemorrhages related to polypoidal choroidal vasculopathy. This Asian woman required vitrectomy to remove vitreous hemorrhage and was seen to have widespread scarring except for the fovea

7.4Common Testing Modalities to Diagnose Choroidal Neovascularization

Each of the specific tests will be covered in much greater detail in subsequent chapters.

7.4.1Fluorescein Angiography

Fluorescein sodium is an orange colored fluorophore that has an excitation maximum of approximately 490 nm. The exact peak varies with a number of factors including the pH and protein concentration in the aqueous solution.

Fluorescein fluoresces at a peak of approximately 520 nm. Fluorescein is used as an ocular angiographic agent. Injection of the dye into the antecubital vein is followed by the eventual appearance of the dye in the ocular vasculature. The choroid fills approximately 1 s before the retinal circulation. The choroidal vasculature is not well visualized with fluorescein angiography because of poor penetration of the excitation wavelengths used and because fluorescein freely diffuses within the choroid. However, fluorescein is excellent at demonstrating the retinal circulation. Ordinarily the dye is constrained by the blood ocular barrier, but in pathologic situations such as CNV, the fluorescein dye not only shows the anatomic changes caused by the new vessel growth but also demonstrates breakdown of the blood ocular barrier by showing leakage.

CNV can be classified into one of several anatomic subtypes. CNV that is seen early and leaks late is called classic CNV. Occult CNV was originally classified as either a fibrovascular PED or late leakage of undetermined source. With modern angiography used in conjunction with OCT, occult CNV is always associated with neovascularization under the RPE.

Occasionally patients will demonstrate CNV both above and below the RPE in what is called minimally classic CNV. At times the retinal circulation may participate in the neovascular process and retinal choroidal anastomosis may be seen. These connections between the retinal and choroidal circulation may best be seen with indocyanine green angiography.

7.4.2Indocyanine Green Angiography

Indocyanine green is a highly protein bound fluorophore with excitation and emission wavelengths that are longer than what are found with fluorescein. As with fluorescein, the peak of the excitation and emission curves varies according to pH and protein concentration. The peak excitation wavelengths are approximately 780–790 nm and the emission peak is approximately 810 nm. These wavelengths penetrate the melanin of the RPE and choroid much more readily than does the wavelengths used by fluorescein angiography. In addition, ICG being highly protein bound is retained within vessels for the most part. These properties allow visualization and characterization of vascularization under the RPE.