Side Effects of ICGA

ICGA has a safer side effect profile compared to FA. Moderate side effects have been reported at a rate of 1:63, serious side effects at a rate of 1:, and death at a rate of 1: after FA.26

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Adverse effects after the use of ICG are rare. Rates of mild, moderate, and severe reactions have been reported as 0.15%, 0.02%, and 0.05-0.07%, respectively.27,28

ICG dye contains up to 5% sodium iodide as an additive to prevent recrystallization. Therefore, caution should be exercised considering the potential side effects in patients with thyroid hyperfunction. Thyroid function tests performed after ICGA give inaccurate results. On the other hand, it is argued that since iodine is naturally found in the human body, there can be no risk of antibody formation or the development of an immune-mediated allergic reaction against it.29 The allergies that develop after consuming shellfish and other seafood are attributed to the proteins in the food, not the iodine.30

The cause of side effects following ICGA has not been fully explained. Non-allergic histamine release due to iodine or ICG, IgE-mediated hypersensitivity, complement system activation, or the release of other inflammation mediators are suggested mechanisms.31

Moreover, although very rare, adequate preparation is necessary in the event of anaphylactic shock after ICG injection.32

ICG dye can also be prepared without the addition of iodine, but severe side effects have also been reported after iodine-free ICGA.33

As ICG separates bilirubin from protein in in vitro studies, it should not be administered to preterm infants and neonates who require transfusion due to hyperbilirubinemia. The indication should also be reviewed in patients with uremia, severe liver failure, or a history of severe multiple allergy (Table 2).3

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Table 2

Table 2. Contraindications of indocyanine green angiography

It has been reported that ICG shows minimal passage across the placenta and that the placenta has a protective effect against its passage to the fetus.34 Although there is no proven teratogenic effect, its indication for use in pregnancy should be carefully discussed.

Non-specific side effects following angiographic dye delivery are usually recorded as allergic reactions. This leads to the restriction of new angiographic examinations needed in the future. For this reason, it is important to reevaluate a patient&#;s history of post-angiography side effects and other possible factors in detail.

Indocyanine green angiography (ICGA) is an imaging technique used to evaluate choroidal vasculature and circulation in which indocyanine green (ICG) dye is injected intravenously. ICG was developed to study cardiac output and hepatic circulation, applied to the field of ophthalmology, and has helped overcome the limitations of sodium fluorescein, the dye used in fluorescein angiography (FA), in the study of choroidal vessels. FA provides great resolution of retinal circulation, but it minimally penetrates the retinal pigment epithelium (RPE), and choroidal circulation is not clearly visualized with this technique.

ICG emits light in the near-infrared spectrum, improving considerably the amount of light that is able to go through the RPE and choroidal pigment, fluid, blood, or lipids. In addition, the majority of the dye binds to plasma proteins, and this property prevents the diffusion of ICG through the fenestrated choriocapillaris, so the dye can accurately delineate choroidal vessels. Also, it is considered a very safe technique, with a very low incidence of adverse reactions. All of these chemical and biophysical properties of ICG make it a very useful tool for the study of choroidal vasculature, especially in those cases in which fluid or blood obscure choroidal details in fluorescein angiogram.

The choroid is a thick and multilayered structure, which constitutes the major blood supply of the eye and receives 90% of the ocular blood flow. The visualization of this complex structure by ICGA can help us expand our current knowledge and understanding of the choroid in the normal eye and also in pathologic conditions. For these reasons, ICGA is a very useful imaging technique in clinical practice.