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Indocyanine green angiography is an important invasive imaging modality among many diagnostic imaging modalities used in retinochoroidal diseases. It helps to study the anatomy, physiology, and pathology of choroidal and retinal circulation. It has an important role in the diagnosis of various ocular pathologies. This activity describes the anatomy of choroidal circulation and reviews the techniques and interpretation of indocyanine green angiography. It also highlights the role of the interprofessional team in monitoring the patient and managing adverse events during the procedure. Objectives: Describe the anatomy and physiology of choroidal circulation. Review the personnel, equipment, preparation, and technique of indocyanine green angiography. Outline the characteristics of various retinal and choroidal diseases on an indocyanine green angiogram. Explain the importance of the availability of an interprofessional team for monitoring the patient and managing complications during indocyanine green angiography. Access free multiple choice questions on this topic.

Indocyanine green angiography (ICGA) is used to image the choroidal circulation and its abnormalities.[1] Even though fundus fluorescein angiography (FFA) is a good tool for imaging retinal circulation in great detail, its ability to image the choroidal circulation is limited by the poor transmission of fluorescence through retinal pigment epithelium (RPE), media opacities, and retinal exudates.[2] The physical characteristics of indocyanine green (ICG) allow its visualization through RPE, lipid exudates, and serosanguineous fluid. Indocyanine green has an absorption peak at 790 to 805 nm and a peak emission spectrum at 835 nm.[3] As its absorption and emission spectrum is of a higher wavelength than that of fluorescein, the infrared rays to and from ICG can penetrate better through the RPE, macular xanthophyll pigments, and media opacities. Also, 98% of ICG in serum is protein-bound, allowing only limited diffusion through the fenestrations of the choriocapillaris, whereas FA diffuses quickly, blurring the anatomy of the choroid.[4][5] ICG was approved for human use by Food and Drug Administration (FDA), the USA, in 1956.[6] ICG angiography (ICGA) of the human choroid was first performed by R W Flower in 1972.[7] Initially, the clarity of images was poor as the ICG molecule has poor fluorescence efficiency compared to FA. But, technological advances in imaging systems (scanning laser ophthalmoscope or SL- based systems) led to the development of high-resolution cameras that could capture ICGA images with great clarity. In the era of anti-vascular endothelial growth factor (anti-VEGF) agents and optical coherence tomography (OCT), the monitoring of the choroidal neovascular membrane (CNVM) has become easier.[8][9] Still, ICGA continues to be an important imaging modality in clinical practice in evaluating various disorders, including idiopathic polypoidal choroidal vasculopathy (IPCV), retinal angiomatous proliferation (RAP), central serous chorioretinopathy (CSCR), ocular inflammatory conditions including sympathetic ophthalmia (SO) and Vogt Koyanagi Harada syndrome (VKH); and ocular tumors.[10][11]

[36]Adverse effects of ICGA are less common compared to FA. Extravasation of the dye can cause a stinging sensation. Mild side effects like nausea and vomiting are seen in 0.15% of patients. Moderate adverse events like urticaria, vasovagal events are seen in 0.2% of patients. Urticaria can be treated using antihistamines. The incidence of severe adverse events is 0.05%. Anaphylaxis can occur in patients with iodine allergies. The incidence of adverse events is more common in patients with uremia compared to the general population.[37]

The team of the ophthalmologist and the assisting nurse takes consent and counsels the patient before the procedure. Pushing the ICG dye while the ophthalmologist or the technician is capturing the images, monitoring the patient for any adverse reactions during the procedure is also carried out by the nursing staff. Anesthetists or critical care specialists are required in cases of severe allergy and anaphylactic reaction. An interprofessional team approach helps to prevent and manage complications. It helps in carrying out ICG angiography with minimal risk.